Snezana Petrovic - Academia.edu (original) (raw)

Papers by Snezana Petrovic

Research paper thumbnail of Missense mutations and proximal RTA. Have we reached a new threshold? Focus on "Missense mutation T485S alters NBCe1-A electrogenicity causing proximal renal tubular acidosis

AJP: Cell Physiology, 2013

Research paper thumbnail of Acid incubation reverses the polarity of intercalated cell transporters, an effect mediated by hensin

Journal of Clinical Investigation, 2002

Research paper thumbnail of Adaptation by the collecting duct to an exogenous acid load is blunted by deletion of the proton-sensing receptor GPR4

American Journal of Physiology - Renal Physiology, 2015

We previously reported that the deletion of the pH sensor GPR4 causes a non-gap metabolic acidosi... more We previously reported that the deletion of the pH sensor GPR4 causes a non-gap metabolic acidosis and defective net acid excretion (NAE) in the GPR4 knockout mouse (GPR4-/-) (Sun X, Yang LV, Tiegs BC, Arend LJ, McGraw DW, Penn RB, and Petrovic S. J Am Soc Nephrol 21: 1745-1755, 2010). Since the major regulatory site of NAE in the kidney is the collecting duct (CD), we examined acid-base transport proteins in intercalated cells (ICs) of the CD and found comparable mRNA expression of kidney anion exchanger 1 (kAE1), pendrin, and the a4 subunit of H(+)-ATPase in GPR4-/- vs. +/+. However, NH4Cl loading elicited adaptive doubling of AE1 mRNA in GPR4+/+, but a 50% less pronounced response in GPR4-/-. In GPR4+/+, NH4Cl loading evoked a cellular response characterized by an increase in AE1-labeled and a decrease in pendrin-labeled ICs similar to what was reported in rabbits and rats. This response did not occur in GPR4-/-. Microperfusion experiments demonstrated that the activity of the basolateral Cl(-)/HCO3(-) exchanger, kAE1, in CDs isolated from GPR4-/- failed to increase with NH4Cl loading, in contrast to the increase observed in GPR4+/+. Therefore, the deficiency of GPR4 blunted, but did not eliminate the adaptive response to an acid load, suggesting a compensatory response from other pH/CO2/bicarbonate sensors. Indeed, the expression of the calcium-sensing receptor (CaSR) was nearly doubled in GPR4-/- kidneys, in the absence of apparent disturbances of Ca(2+) homeostasis. In summary, the expression and activity of the key transport proteins in GPR4-/- mice are consistent with spontaneous metabolic acidosis, but the adaptive response to a superimposed exogenous acid load is blunted and might be partially compensated for by CaSR.

Research paper thumbnail of Regulation of the apical Cl-/HCO-3 exchanger pendrin in rat cortical collecting duct in metabolic acidosis

American journal of physiology. Renal physiology, 2003

Pendrin is an apical Cl(-)/OH(-)/HCO(3)(-) exchanger in beta-intercalated cells (beta-ICs) of rat... more Pendrin is an apical Cl(-)/OH(-)/HCO(3)(-) exchanger in beta-intercalated cells (beta-ICs) of rat and mouse cortical collecting duct (CCD). However, little is known about its regulation in acid-base disorders. Here, we examined the regulation of pendrin in metabolic acidosis, a condition known to decrease HCO(3)(-) secretion in CCD. Rats were subjected to NH(4)Cl loading for 4 days, which resulted in metabolic acidosis. Apical Cl(-)/HCO(3)(-) exchanger activity in beta-ICs was determined as amplitude and rate of intracellular pH change when Cl was removed in isolated, microperfused CCDs. Intracellular pH was measured by single-cell digital ratiometric imaging using fluorescent pH-sensitive dye 2',7'-bis-(3-carboxypropyl)-5-(and-6)-carboxyfluorescein-AM. Pendrin mRNA expression in kidney cortex was examined by Northern blot hybridizations. Expression of pendrin protein was assessed by indirect immunofluorescence. Microperfused CCDs isolated from acidotic rats demonstrated app...

Research paper thumbnail of Identification of an apical Cl-/HCO-3 exchanger in rat kidney proximal tubule

American journal of physiology. Cell physiology, 2003

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney... more SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates Cl-/HCO3- exchange in in vitro expression systems. We hypothesized that PAT1 along with a Cl-/HCO3- exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical Cl-/HCO3- exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit Na+-HCO3- c...

Research paper thumbnail of Colocalization of the apical Cl-/HCO3- exchanger PAT1 and gastric H-K-ATPase in stomach parietal cells

American journal of physiology. Gastrointestinal and liver physiology, 2002

The apical Cl-/HCO exchanger called the putative anion transporter (PAT1; SLC26A6) is expressed o... more The apical Cl-/HCO exchanger called the putative anion transporter (PAT1; SLC26A6) is expressed on apical membranes of villus cells in the duodenum, but its location in the stomach remains unknown. Here we examined the cell distribution and membrane location of PAT1 in mouse stomach. Immunofluorescence labeling studies with anti-PAT1 antibodies and Dolichos biflorus agglutinin indicated the exclusive expression of PAT1 in gastric parietal cells. Double immunocytochemical staining revealed colocalization of PAT1 with the gastric H-K-ATPase, consistent with expression in tubulovesicles and/or the secretory canaliculus. Radiolabeled 36Cl flux studies demonstrated the functional presence of Cl-/HCO exchange in purified tubulovesicles of parietal cells. The expression of PAT1 was significantly decreased in parietal cells of gastric H-K-ATPase-null mice, which exhibit a sharp reduction in tubulovesicle membranes. These data indicate that the Cl-/HCO exchanger PAT1 is localized on tubulove...

Research paper thumbnail of Novel Schering and ouabain-insensitive potassium-dependent proton secretion in the mouse cortical collecting duct

American journal of physiology. Renal physiology, 2002

The intercalated (IC) cells of the cortical collecting duct (CCD) are important to acid-base home... more The intercalated (IC) cells of the cortical collecting duct (CCD) are important to acid-base homeostasis by secreting acid and reabsorbing bicarbonate. Acid secretion is mediated predominantly by apical membrane Schering (SCH-28080)-sensitive H(+)-K(+)- ATPase (HKA) and bafilomycin-sensitive H(+)-ATPase. The SCH-28080-sensitive HKA is believed to be the gastric HKA (HKAg). Here we examined apical membrane potassium-dependent proton secretion in IC cells of wild-type HKAg (+/+) and HKAg knockout (-/-) mice to determine relative contribution of HKAg to luminal proton secretion. The results demonstrated that HKAg (-/-) and wild-type mice had comparable rates of potassium-dependent proton secretion, with HKAg (-/-) mice having 100% of K(+)-dependent H(+) secretion vs. wild-type mice. Potassium-dependent proton secretion was resistant to ouabain and SCH-28080 in HKAg knockout mice but was sensitive to SCH-28080 in wild-type animals. Northern hybridizations did not demonstrate any upregul...

Research paper thumbnail of The lexicon manuscript by Dimitrije Cemerikic as a source for ethnolinguistic and ethnologic research

Glasnik Etnografskog instituta, 2014

Research paper thumbnail of Identification of an apical Cl-/HCO3- exchanger in gastric surface mucous and duodenal villus cells

American journal of physiology. Gastrointestinal and liver physiology, 2003

The molecular identity of the apical HCO3(-)-secreting transporter in gastric mucous cells remain... more The molecular identity of the apical HCO3(-)-secreting transporter in gastric mucous cells remains unknown despite its essential role in preventing injury and ulcer by gastric acid. Here we report the identification of a Cl-/HCO3- exchanger that is located on apical membranes of gastric surface epithelial cells. RT-PCR studies of mouse gastrointestinal tract mRNAs demonstrated that this transporter, known as anion exchanger isoform 4 (AE4), is expressed in both stomach and duodenum. Northern blot analysis of RNA from purified stomach epithelial cells indicated that AE4 is expressed at higher levels in mucous cells than in parietal cells. Immunoblotting experiments identified AE4 as a approximately 110- to 120-kDa protein in membranes from stomach epithelium and apical membranes from duodenum. Immunocytochemical staining demonstrated that AE4 is expressed in apical membranes of surface cells in both mouse and rabbit stomach and duodenum. Functional studies in oocytes indicated that A...

Research paper thumbnail of Femtosecond laser modification of multilayered TiAlN/TiN coating

Surface and Coatings Technology, 2011

A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200fs pulses of a... more A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200fs pulses of a Ti:Sapphire laser, operating at 775nm. Laser fluences of 1.16Jcm−2 to 116Jcm−2 produced a range of modifications, from well defined parallel surface structures on the coating, to deep craters in the substrate. Parameters for coating ablation were determined in terms of laser fluence and pulse

Research paper thumbnail of The Expression of Na+:HCO3 - Cotransporter NBC4 in Rat Kidney and Characterization of a Novel NBC4 Variant

Research paper thumbnail of A Basis of Enhanced Fluid and Electrolyte Reabsorption By Formate in the Kidney Proximal Tubule

Formate stimulates sodium chloride and fluid reabsorption in kidney proximal tubule, however, the... more Formate stimulates sodium chloride and fluid reabsorption in kidney proximal tubule, however, the exact cellular mechanism of this effect remains unknown. We hypothesized that the primary target of formate,is the apical Na, exchanger ,(NHE3) activity in mouse kidney proximal tubule. In the absence of CO2/HCO3 -

Research paper thumbnail of Mouse Na+: HCO3- cotransporter isoform NBC-3 (kNBC-3): Cloning, expression, and renal distribution

Kidney International, 2001

cess of sodium bicarbonate cotransport has an important Cloning, expression, and renal distribution.

Research paper thumbnail of Differential Regulation of Basolateral Cl-/HCO3- Exchangers SLC26A7 and AE1 in Kidney Outer Medullary Collecting Duct

Journal of the American Society of Nephrology, 2004

SLC26A7 is a recently identified Cl Ϫ /HCO 3 Ϫ exchanger that co-localizes with AE1 on the basola... more SLC26A7 is a recently identified Cl Ϫ /HCO 3 Ϫ exchanger that co-localizes with AE1 on the basolateral membrane of 〈 intercalated cells (A-IC) in outer medullary collecting duct (OMCD). The purpose of these studies was to determine whether AE1 and SLC26A7 are differentially regulated in OMCD in pathophysiologic states. Toward this end, the expression and regulation of AE1 and SLC26A7 was examined in water deprivation, a condition known to increase the osmolality of the medulla. Rats were subjected to 3 d of water deprivation while having free access to food. Northern hybridizations demonstrated that in the outer medulla, the mRNA expression of SLC26A7 increased by~300% (P Ͻ 0.01 versus control; n ϭ 3), whereas the expression of AE1 decreased by~50% (P Ͻ 0.05 versus control, n ϭ 3) in water-deprived rats. Immunoblot analysis studies demonstrated that in the outer medulla, SLC26A7 abundance increased by~3

Research paper thumbnail of Chloride/Bicarbonate Exchanger SLC26A7 Is Localized in Endosomes in Medullary Collecting Duct Cells and Is Targeted to the Basolateral Membrane in Hypertonicity and Potassium Depletion

Journal of the American Society of Nephrology, 2006

SLC26A7 is a Cl(-)/HCO(3)(-) exchanger that is expressed on the basolateral membrane and in the c... more SLC26A7 is a Cl(-)/HCO(3)(-) exchanger that is expressed on the basolateral membrane and in the cytoplasm of two distinct acid-secreting epithelial cells: The A-intercalated cells in the kidney outer medullary collecting duct and the gastric parietal cells. The intracellular localization of SLC26A7 suggests the possibility of trafficking between cell membrane and intracellular compartments. For testing this hypothesis, full-length human SLC26A7 cDNA was fused with green fluorescence protein and transiently expressed in MDCK epithelial cells. In monolayer cells in isotonic medium, SLC26A7 showed punctate distribution throughout the cytoplasm. However, in medium that was made hypertonic for 16 h, SLC26A7 was detected predominantly in the plasma membrane. The presence of mitogen-activated protein kinase inhibitors blocked the trafficking of SLC26A7 to the plasma membrane. Double-labeling studies demonstrated the localization of SLC26A7 to the transferrin receptor-positive endosomes. A chimera that was composed of the amino terminal fragment of SLC26A7 and the carboxyl terminal fragment of SLC26A1, and a C-terminal-truncated SLC26A7 were retained in the cytoplasm in hypertonicity. In separate studies, SLC26A7 showed predominant localization in plasma membrane in potassium-depleted isotonic medium (0.5 or 2 mEq/L KCl) versus cytoplasmic distribution in normal potassium isotonic medium (4 mEq/L). It is concluded that SLC26A7 is present in endosomes, and its targeting to the basolateral membrane is increased in hypertonicity and potassium depletion. The trafficking to the cell surface suggests novel functional upregulation of SLC26A7 in states that are associated with hypokalemia or increased medullary tonicity. Additional studies are needed to ascertain the role of SLC26A7 in enhanced bicarbonate absorption in outer medullary collecting duct in hypokalemia and in acid-base regulation in conditions that are associated with increased medullary tonicity.

Research paper thumbnail of Acid incubation reverses the polarity of intercalated cell transporters, an effect mediated by hensin

Journal of Clinical Investigation, 2002

Metabolic acidosis causes a reversal of polarity of HCO 3flux in the cortical collecting duct (CC... more Metabolic acidosis causes a reversal of polarity of HCO 3flux in the cortical collecting duct (CCD). In CCDs incubated in vitro in acid media, β-intercalated (HCO 3 --secreting) cells are remodeled to functionally resemble α-intercalated (H + -secreting) cells. A similar remodeling of β-intercalated cells, in which the polarity of H + pumps and Cl -/HCO 3exchangers is reversed, occurs in cell culture and requires the deposition of polymerized hensin in the ECM. CCDs maintained 3 h at low pH ex vivo display a reversal of HCO 3flux that is quantitatively similar to an effect previously observed in acidtreated rabbits in vivo. We followed intracellular pH in the same β-intercalated cells before and after acid incubation and found that apical Cl/HCO 3 exchange was abolished following acid incubation. Some cells also developed basolateral Cl -/HCO 3exchange, indicating a reversal of intercalated cell polarity. This adaptation required intact microtubules and microfilaments, as well as new protein synthesis, and was associated with decreased size of the apical surface of β-intercalated cells. Addition of anti-hensin antibodies prevented the acid-induced changes in apical and basolateral Cl -/HCO 3exchange observed in the same cells and the corresponding suppression of HCO 3secretion. Acid loading also promoted hensin deposition in the ECM underneath adapting β-intercalated cells. Hence, the adaptive conversion of β-intercalated cells to α-intercalated cells during acid incubation depends upon ECM-associated hensin.

Research paper thumbnail of Identification of a basolateral Cl-/HCO3- exchanger specific to gastric parietal cells

Gastroenterology, 2003

The basolateral Cl(-)/HCO(3)(-) exchanger in parietal cells plays an essential role in gastric ac... more The basolateral Cl(-)/HCO(3)(-) exchanger in parietal cells plays an essential role in gastric acid secretion mediated via the apical gastric H(+)-K(+)-ATPase. Here, we report the identification of a new Cl(-)/HCO(3)(-) exchanger, which shows exclusive expression in mouse stomach and kidney, with expression in the stomach limited to the basolateral membrane of gastric parietal cells. Tissue distribution studies by RT-PCR and Northern hybridizations demonstrated the exclusive expression of this transporter, also known as SLC26A7, to stomach and kidney, with the stomach expression significantly more abundant. No expression was detected in the intestine. Cellular distribution studies by RT-PCR and Northern hybridizations demonstrated predominant localization of SLC26A7 in gastric parietal cells. Immunofluorescence labeling localized this exchanger exclusively to the basolateral membrane of gastric parietal cells, and functional studies in oocytes indicated that SLC26A7 is a DIDS-sensitive Cl(-)/HCO(3)(-) exchanger that is active in both acidic and alkaline pH(i). On the basis of its unique expression pattern and function, we propose that SLC26A7 is a basolateral Cl(-)/HCO(3)(-) exchanger in gastric parietal cells and plays a major role in gastric acid secretion.

Research paper thumbnail of Role of basolateral carbonic anhydrase in proximal tubular fluid and bicarbonate absorption

American Journal of …, 2001

ABSTRACT Membrane-bound carbonic anhydrase (CA) is critical to renal acidification. The role of C... more ABSTRACT Membrane-bound carbonic anhydrase (CA) is critical to renal acidification. The role of CA activity on the basolateral membrane of the proximal tubule has not been defined clearly. To investigate this issue in microperfused rabbit proximal straight tubules in vitro, we measured fluid and HCO(3)(-) absorption and cell pH before and after the extracellular CA inhibitor p-fluorobenzyl-aminobenzolamide was applied in the bath to inhibit only basolateral CA. This inhibitor was 1% as permeant as acetazolamide. Neutral dextran (2 g/dl, molecular mass 70,000) was used as a colloid to support fluid absorption because albumin could affect CO(2) diffusion and rheogenic HCO(3)(-) efflux. Indeed, dextran in the bath stimulated fluid absorption by 55% over albumin. Basolateral CA inhibition reduced fluid absorption ( approximately 30%) and markedly decreased HCO(3)(-) absorption ( approximately 60%), both reversible when CA was added to the bathing solution. In the presence of luminal CA inhibition, which reduced fluid ( approximately 16%) and HCO(3)(-) ( approximately 66%) absorption, inhibition of basolateral CA further decreased the absorption of fluid (to 74% of baseline) and HCO(3)(-) (to 22% of baseline). CA inhibition also alkalinized cell pH by approximately 0.2 units, suggesting the presence of an alkaline disequilibrium pH in the interspace, which would secondarily block HCO(3)(-) exit from the cell and thereby decrease luminal proton secretion (HCO(3)(-) absorption). These data clearly indicate that basolateral CA has an important role in mediating fluid and especially HCO(3)(-) absorption in the proximal straight tubule.

Research paper thumbnail of Composition and structure modification of a WTi/Si system by short laser pulses

Applied Physics A, 2010

Picosecond (40 ps) pulsed Nd:YAG laser irradiation of a WTi thin film on silicon with a wavelengt... more Picosecond (40 ps) pulsed Nd:YAG laser irradiation of a WTi thin film on silicon with a wavelength of 532 nm and a fluence 2.1 J/cm 2 was performed in air. This led to significant changes of the chemical composition and morphology on the surface of the WTi thin film. The results show an increase in surface roughness, due to formation of conical structures, about 50 nm wide in the base, and a very thin oxide layer composed of WO 3 and TiO 2 , with a dominant TiO 2 phase at the top, within the depth of about 20 nm. The thickness of the oxide layer was dependent on the number of laser pulses. The samples were analyzed by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy.

Research paper thumbnail of Vasopressin induces expression of the Cl-/HCO3- exchanger SLC26A7 in kidney medullary collecting ducts of Brattleboro rats

AJP: Renal Physiology, 2005

SLC26A7 is a newly identified basolateral Cl(-)/HCO(3)(-) exchanger specific to alpha-intercalate... more SLC26A7 is a newly identified basolateral Cl(-)/HCO(3)(-) exchanger specific to alpha-intercalated cells of the outer medullary collecting duct (OMCD). The purpose of the present experiments was to examine the expression of SLC26A7 in kidneys of vasopressin-deficient Brattleboro rats before and after treatment with desamino-Cys(1),d-Arg(8)-vasopressin (dDAVP). Brattleboro rats were treated with dDAVP, a vasopressin analog, for 8 days, and their kidneys were examined for the expression of SLC26A7. The expression of SLC26A7 protein, as examined by immunofluorescence, was undetectable in kidneys of Brattleboro rats. However, treatment with dDAVP induced expression of SLC26A7 protein, restoring it to levels observed in normal rats. These results were verified by Western blot analysis. The mRNA expression of SLC26A7 remained unchanged in response to dDAVP. Immunofluorescent labeling demonstrated abundant levels of anion exchanger type 1 in the OMCD of Brattleboro rats and a mild reduction in response to dDAVP. The abundance of H(+)-ATPase was not affected by dDAVP. The increased SLC26A7 expression directly correlated with enhanced aquaporin-2 expression, which is proportional to increased interstitial osmolarity in the medulla. In conclusion, vasopressin increases the expression of SLC26A7 protein through posttranscriptional mechanisms in the OMCD. The induction of SLC26A7 by vasopressin in OMCD cells of Brattleboro rats is likely an attempt by cells to regulate their cell volume and maintain HCO(3)(-) absorption in a state associated with increased interstitial medullary tonicity.

Research paper thumbnail of Missense mutations and proximal RTA. Have we reached a new threshold? Focus on "Missense mutation T485S alters NBCe1-A electrogenicity causing proximal renal tubular acidosis

AJP: Cell Physiology, 2013

Research paper thumbnail of Acid incubation reverses the polarity of intercalated cell transporters, an effect mediated by hensin

Journal of Clinical Investigation, 2002

Research paper thumbnail of Adaptation by the collecting duct to an exogenous acid load is blunted by deletion of the proton-sensing receptor GPR4

American Journal of Physiology - Renal Physiology, 2015

We previously reported that the deletion of the pH sensor GPR4 causes a non-gap metabolic acidosi... more We previously reported that the deletion of the pH sensor GPR4 causes a non-gap metabolic acidosis and defective net acid excretion (NAE) in the GPR4 knockout mouse (GPR4-/-) (Sun X, Yang LV, Tiegs BC, Arend LJ, McGraw DW, Penn RB, and Petrovic S. J Am Soc Nephrol 21: 1745-1755, 2010). Since the major regulatory site of NAE in the kidney is the collecting duct (CD), we examined acid-base transport proteins in intercalated cells (ICs) of the CD and found comparable mRNA expression of kidney anion exchanger 1 (kAE1), pendrin, and the a4 subunit of H(+)-ATPase in GPR4-/- vs. +/+. However, NH4Cl loading elicited adaptive doubling of AE1 mRNA in GPR4+/+, but a 50% less pronounced response in GPR4-/-. In GPR4+/+, NH4Cl loading evoked a cellular response characterized by an increase in AE1-labeled and a decrease in pendrin-labeled ICs similar to what was reported in rabbits and rats. This response did not occur in GPR4-/-. Microperfusion experiments demonstrated that the activity of the basolateral Cl(-)/HCO3(-) exchanger, kAE1, in CDs isolated from GPR4-/- failed to increase with NH4Cl loading, in contrast to the increase observed in GPR4+/+. Therefore, the deficiency of GPR4 blunted, but did not eliminate the adaptive response to an acid load, suggesting a compensatory response from other pH/CO2/bicarbonate sensors. Indeed, the expression of the calcium-sensing receptor (CaSR) was nearly doubled in GPR4-/- kidneys, in the absence of apparent disturbances of Ca(2+) homeostasis. In summary, the expression and activity of the key transport proteins in GPR4-/- mice are consistent with spontaneous metabolic acidosis, but the adaptive response to a superimposed exogenous acid load is blunted and might be partially compensated for by CaSR.

Research paper thumbnail of Regulation of the apical Cl-/HCO-3 exchanger pendrin in rat cortical collecting duct in metabolic acidosis

American journal of physiology. Renal physiology, 2003

Pendrin is an apical Cl(-)/OH(-)/HCO(3)(-) exchanger in beta-intercalated cells (beta-ICs) of rat... more Pendrin is an apical Cl(-)/OH(-)/HCO(3)(-) exchanger in beta-intercalated cells (beta-ICs) of rat and mouse cortical collecting duct (CCD). However, little is known about its regulation in acid-base disorders. Here, we examined the regulation of pendrin in metabolic acidosis, a condition known to decrease HCO(3)(-) secretion in CCD. Rats were subjected to NH(4)Cl loading for 4 days, which resulted in metabolic acidosis. Apical Cl(-)/HCO(3)(-) exchanger activity in beta-ICs was determined as amplitude and rate of intracellular pH change when Cl was removed in isolated, microperfused CCDs. Intracellular pH was measured by single-cell digital ratiometric imaging using fluorescent pH-sensitive dye 2',7'-bis-(3-carboxypropyl)-5-(and-6)-carboxyfluorescein-AM. Pendrin mRNA expression in kidney cortex was examined by Northern blot hybridizations. Expression of pendrin protein was assessed by indirect immunofluorescence. Microperfused CCDs isolated from acidotic rats demonstrated app...

Research paper thumbnail of Identification of an apical Cl-/HCO-3 exchanger in rat kidney proximal tubule

American journal of physiology. Cell physiology, 2003

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney... more SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates Cl-/HCO3- exchange in in vitro expression systems. We hypothesized that PAT1 along with a Cl-/HCO3- exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical Cl-/HCO3- exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit Na+-HCO3- c...

Research paper thumbnail of Colocalization of the apical Cl-/HCO3- exchanger PAT1 and gastric H-K-ATPase in stomach parietal cells

American journal of physiology. Gastrointestinal and liver physiology, 2002

The apical Cl-/HCO exchanger called the putative anion transporter (PAT1; SLC26A6) is expressed o... more The apical Cl-/HCO exchanger called the putative anion transporter (PAT1; SLC26A6) is expressed on apical membranes of villus cells in the duodenum, but its location in the stomach remains unknown. Here we examined the cell distribution and membrane location of PAT1 in mouse stomach. Immunofluorescence labeling studies with anti-PAT1 antibodies and Dolichos biflorus agglutinin indicated the exclusive expression of PAT1 in gastric parietal cells. Double immunocytochemical staining revealed colocalization of PAT1 with the gastric H-K-ATPase, consistent with expression in tubulovesicles and/or the secretory canaliculus. Radiolabeled 36Cl flux studies demonstrated the functional presence of Cl-/HCO exchange in purified tubulovesicles of parietal cells. The expression of PAT1 was significantly decreased in parietal cells of gastric H-K-ATPase-null mice, which exhibit a sharp reduction in tubulovesicle membranes. These data indicate that the Cl-/HCO exchanger PAT1 is localized on tubulove...

Research paper thumbnail of Novel Schering and ouabain-insensitive potassium-dependent proton secretion in the mouse cortical collecting duct

American journal of physiology. Renal physiology, 2002

The intercalated (IC) cells of the cortical collecting duct (CCD) are important to acid-base home... more The intercalated (IC) cells of the cortical collecting duct (CCD) are important to acid-base homeostasis by secreting acid and reabsorbing bicarbonate. Acid secretion is mediated predominantly by apical membrane Schering (SCH-28080)-sensitive H(+)-K(+)- ATPase (HKA) and bafilomycin-sensitive H(+)-ATPase. The SCH-28080-sensitive HKA is believed to be the gastric HKA (HKAg). Here we examined apical membrane potassium-dependent proton secretion in IC cells of wild-type HKAg (+/+) and HKAg knockout (-/-) mice to determine relative contribution of HKAg to luminal proton secretion. The results demonstrated that HKAg (-/-) and wild-type mice had comparable rates of potassium-dependent proton secretion, with HKAg (-/-) mice having 100% of K(+)-dependent H(+) secretion vs. wild-type mice. Potassium-dependent proton secretion was resistant to ouabain and SCH-28080 in HKAg knockout mice but was sensitive to SCH-28080 in wild-type animals. Northern hybridizations did not demonstrate any upregul...

Research paper thumbnail of The lexicon manuscript by Dimitrije Cemerikic as a source for ethnolinguistic and ethnologic research

Glasnik Etnografskog instituta, 2014

Research paper thumbnail of Identification of an apical Cl-/HCO3- exchanger in gastric surface mucous and duodenal villus cells

American journal of physiology. Gastrointestinal and liver physiology, 2003

The molecular identity of the apical HCO3(-)-secreting transporter in gastric mucous cells remain... more The molecular identity of the apical HCO3(-)-secreting transporter in gastric mucous cells remains unknown despite its essential role in preventing injury and ulcer by gastric acid. Here we report the identification of a Cl-/HCO3- exchanger that is located on apical membranes of gastric surface epithelial cells. RT-PCR studies of mouse gastrointestinal tract mRNAs demonstrated that this transporter, known as anion exchanger isoform 4 (AE4), is expressed in both stomach and duodenum. Northern blot analysis of RNA from purified stomach epithelial cells indicated that AE4 is expressed at higher levels in mucous cells than in parietal cells. Immunoblotting experiments identified AE4 as a approximately 110- to 120-kDa protein in membranes from stomach epithelium and apical membranes from duodenum. Immunocytochemical staining demonstrated that AE4 is expressed in apical membranes of surface cells in both mouse and rabbit stomach and duodenum. Functional studies in oocytes indicated that A...

Research paper thumbnail of Femtosecond laser modification of multilayered TiAlN/TiN coating

Surface and Coatings Technology, 2011

A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200fs pulses of a... more A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200fs pulses of a Ti:Sapphire laser, operating at 775nm. Laser fluences of 1.16Jcm−2 to 116Jcm−2 produced a range of modifications, from well defined parallel surface structures on the coating, to deep craters in the substrate. Parameters for coating ablation were determined in terms of laser fluence and pulse

Research paper thumbnail of The Expression of Na+:HCO3 - Cotransporter NBC4 in Rat Kidney and Characterization of a Novel NBC4 Variant

Research paper thumbnail of A Basis of Enhanced Fluid and Electrolyte Reabsorption By Formate in the Kidney Proximal Tubule

Formate stimulates sodium chloride and fluid reabsorption in kidney proximal tubule, however, the... more Formate stimulates sodium chloride and fluid reabsorption in kidney proximal tubule, however, the exact cellular mechanism of this effect remains unknown. We hypothesized that the primary target of formate,is the apical Na, exchanger ,(NHE3) activity in mouse kidney proximal tubule. In the absence of CO2/HCO3 -

Research paper thumbnail of Mouse Na+: HCO3- cotransporter isoform NBC-3 (kNBC-3): Cloning, expression, and renal distribution

Kidney International, 2001

cess of sodium bicarbonate cotransport has an important Cloning, expression, and renal distribution.

Research paper thumbnail of Differential Regulation of Basolateral Cl-/HCO3- Exchangers SLC26A7 and AE1 in Kidney Outer Medullary Collecting Duct

Journal of the American Society of Nephrology, 2004

SLC26A7 is a recently identified Cl Ϫ /HCO 3 Ϫ exchanger that co-localizes with AE1 on the basola... more SLC26A7 is a recently identified Cl Ϫ /HCO 3 Ϫ exchanger that co-localizes with AE1 on the basolateral membrane of 〈 intercalated cells (A-IC) in outer medullary collecting duct (OMCD). The purpose of these studies was to determine whether AE1 and SLC26A7 are differentially regulated in OMCD in pathophysiologic states. Toward this end, the expression and regulation of AE1 and SLC26A7 was examined in water deprivation, a condition known to increase the osmolality of the medulla. Rats were subjected to 3 d of water deprivation while having free access to food. Northern hybridizations demonstrated that in the outer medulla, the mRNA expression of SLC26A7 increased by~300% (P Ͻ 0.01 versus control; n ϭ 3), whereas the expression of AE1 decreased by~50% (P Ͻ 0.05 versus control, n ϭ 3) in water-deprived rats. Immunoblot analysis studies demonstrated that in the outer medulla, SLC26A7 abundance increased by~3

Research paper thumbnail of Chloride/Bicarbonate Exchanger SLC26A7 Is Localized in Endosomes in Medullary Collecting Duct Cells and Is Targeted to the Basolateral Membrane in Hypertonicity and Potassium Depletion

Journal of the American Society of Nephrology, 2006

SLC26A7 is a Cl(-)/HCO(3)(-) exchanger that is expressed on the basolateral membrane and in the c... more SLC26A7 is a Cl(-)/HCO(3)(-) exchanger that is expressed on the basolateral membrane and in the cytoplasm of two distinct acid-secreting epithelial cells: The A-intercalated cells in the kidney outer medullary collecting duct and the gastric parietal cells. The intracellular localization of SLC26A7 suggests the possibility of trafficking between cell membrane and intracellular compartments. For testing this hypothesis, full-length human SLC26A7 cDNA was fused with green fluorescence protein and transiently expressed in MDCK epithelial cells. In monolayer cells in isotonic medium, SLC26A7 showed punctate distribution throughout the cytoplasm. However, in medium that was made hypertonic for 16 h, SLC26A7 was detected predominantly in the plasma membrane. The presence of mitogen-activated protein kinase inhibitors blocked the trafficking of SLC26A7 to the plasma membrane. Double-labeling studies demonstrated the localization of SLC26A7 to the transferrin receptor-positive endosomes. A chimera that was composed of the amino terminal fragment of SLC26A7 and the carboxyl terminal fragment of SLC26A1, and a C-terminal-truncated SLC26A7 were retained in the cytoplasm in hypertonicity. In separate studies, SLC26A7 showed predominant localization in plasma membrane in potassium-depleted isotonic medium (0.5 or 2 mEq/L KCl) versus cytoplasmic distribution in normal potassium isotonic medium (4 mEq/L). It is concluded that SLC26A7 is present in endosomes, and its targeting to the basolateral membrane is increased in hypertonicity and potassium depletion. The trafficking to the cell surface suggests novel functional upregulation of SLC26A7 in states that are associated with hypokalemia or increased medullary tonicity. Additional studies are needed to ascertain the role of SLC26A7 in enhanced bicarbonate absorption in outer medullary collecting duct in hypokalemia and in acid-base regulation in conditions that are associated with increased medullary tonicity.

Research paper thumbnail of Acid incubation reverses the polarity of intercalated cell transporters, an effect mediated by hensin

Journal of Clinical Investigation, 2002

Metabolic acidosis causes a reversal of polarity of HCO 3flux in the cortical collecting duct (CC... more Metabolic acidosis causes a reversal of polarity of HCO 3flux in the cortical collecting duct (CCD). In CCDs incubated in vitro in acid media, β-intercalated (HCO 3 --secreting) cells are remodeled to functionally resemble α-intercalated (H + -secreting) cells. A similar remodeling of β-intercalated cells, in which the polarity of H + pumps and Cl -/HCO 3exchangers is reversed, occurs in cell culture and requires the deposition of polymerized hensin in the ECM. CCDs maintained 3 h at low pH ex vivo display a reversal of HCO 3flux that is quantitatively similar to an effect previously observed in acidtreated rabbits in vivo. We followed intracellular pH in the same β-intercalated cells before and after acid incubation and found that apical Cl/HCO 3 exchange was abolished following acid incubation. Some cells also developed basolateral Cl -/HCO 3exchange, indicating a reversal of intercalated cell polarity. This adaptation required intact microtubules and microfilaments, as well as new protein synthesis, and was associated with decreased size of the apical surface of β-intercalated cells. Addition of anti-hensin antibodies prevented the acid-induced changes in apical and basolateral Cl -/HCO 3exchange observed in the same cells and the corresponding suppression of HCO 3secretion. Acid loading also promoted hensin deposition in the ECM underneath adapting β-intercalated cells. Hence, the adaptive conversion of β-intercalated cells to α-intercalated cells during acid incubation depends upon ECM-associated hensin.

Research paper thumbnail of Identification of a basolateral Cl-/HCO3- exchanger specific to gastric parietal cells

Gastroenterology, 2003

The basolateral Cl(-)/HCO(3)(-) exchanger in parietal cells plays an essential role in gastric ac... more The basolateral Cl(-)/HCO(3)(-) exchanger in parietal cells plays an essential role in gastric acid secretion mediated via the apical gastric H(+)-K(+)-ATPase. Here, we report the identification of a new Cl(-)/HCO(3)(-) exchanger, which shows exclusive expression in mouse stomach and kidney, with expression in the stomach limited to the basolateral membrane of gastric parietal cells. Tissue distribution studies by RT-PCR and Northern hybridizations demonstrated the exclusive expression of this transporter, also known as SLC26A7, to stomach and kidney, with the stomach expression significantly more abundant. No expression was detected in the intestine. Cellular distribution studies by RT-PCR and Northern hybridizations demonstrated predominant localization of SLC26A7 in gastric parietal cells. Immunofluorescence labeling localized this exchanger exclusively to the basolateral membrane of gastric parietal cells, and functional studies in oocytes indicated that SLC26A7 is a DIDS-sensitive Cl(-)/HCO(3)(-) exchanger that is active in both acidic and alkaline pH(i). On the basis of its unique expression pattern and function, we propose that SLC26A7 is a basolateral Cl(-)/HCO(3)(-) exchanger in gastric parietal cells and plays a major role in gastric acid secretion.

Research paper thumbnail of Role of basolateral carbonic anhydrase in proximal tubular fluid and bicarbonate absorption

American Journal of …, 2001

ABSTRACT Membrane-bound carbonic anhydrase (CA) is critical to renal acidification. The role of C... more ABSTRACT Membrane-bound carbonic anhydrase (CA) is critical to renal acidification. The role of CA activity on the basolateral membrane of the proximal tubule has not been defined clearly. To investigate this issue in microperfused rabbit proximal straight tubules in vitro, we measured fluid and HCO(3)(-) absorption and cell pH before and after the extracellular CA inhibitor p-fluorobenzyl-aminobenzolamide was applied in the bath to inhibit only basolateral CA. This inhibitor was 1% as permeant as acetazolamide. Neutral dextran (2 g/dl, molecular mass 70,000) was used as a colloid to support fluid absorption because albumin could affect CO(2) diffusion and rheogenic HCO(3)(-) efflux. Indeed, dextran in the bath stimulated fluid absorption by 55% over albumin. Basolateral CA inhibition reduced fluid absorption ( approximately 30%) and markedly decreased HCO(3)(-) absorption ( approximately 60%), both reversible when CA was added to the bathing solution. In the presence of luminal CA inhibition, which reduced fluid ( approximately 16%) and HCO(3)(-) ( approximately 66%) absorption, inhibition of basolateral CA further decreased the absorption of fluid (to 74% of baseline) and HCO(3)(-) (to 22% of baseline). CA inhibition also alkalinized cell pH by approximately 0.2 units, suggesting the presence of an alkaline disequilibrium pH in the interspace, which would secondarily block HCO(3)(-) exit from the cell and thereby decrease luminal proton secretion (HCO(3)(-) absorption). These data clearly indicate that basolateral CA has an important role in mediating fluid and especially HCO(3)(-) absorption in the proximal straight tubule.

Research paper thumbnail of Composition and structure modification of a WTi/Si system by short laser pulses

Applied Physics A, 2010

Picosecond (40 ps) pulsed Nd:YAG laser irradiation of a WTi thin film on silicon with a wavelengt... more Picosecond (40 ps) pulsed Nd:YAG laser irradiation of a WTi thin film on silicon with a wavelength of 532 nm and a fluence 2.1 J/cm 2 was performed in air. This led to significant changes of the chemical composition and morphology on the surface of the WTi thin film. The results show an increase in surface roughness, due to formation of conical structures, about 50 nm wide in the base, and a very thin oxide layer composed of WO 3 and TiO 2 , with a dominant TiO 2 phase at the top, within the depth of about 20 nm. The thickness of the oxide layer was dependent on the number of laser pulses. The samples were analyzed by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy.

Research paper thumbnail of Vasopressin induces expression of the Cl-/HCO3- exchanger SLC26A7 in kidney medullary collecting ducts of Brattleboro rats

AJP: Renal Physiology, 2005

SLC26A7 is a newly identified basolateral Cl(-)/HCO(3)(-) exchanger specific to alpha-intercalate... more SLC26A7 is a newly identified basolateral Cl(-)/HCO(3)(-) exchanger specific to alpha-intercalated cells of the outer medullary collecting duct (OMCD). The purpose of the present experiments was to examine the expression of SLC26A7 in kidneys of vasopressin-deficient Brattleboro rats before and after treatment with desamino-Cys(1),d-Arg(8)-vasopressin (dDAVP). Brattleboro rats were treated with dDAVP, a vasopressin analog, for 8 days, and their kidneys were examined for the expression of SLC26A7. The expression of SLC26A7 protein, as examined by immunofluorescence, was undetectable in kidneys of Brattleboro rats. However, treatment with dDAVP induced expression of SLC26A7 protein, restoring it to levels observed in normal rats. These results were verified by Western blot analysis. The mRNA expression of SLC26A7 remained unchanged in response to dDAVP. Immunofluorescent labeling demonstrated abundant levels of anion exchanger type 1 in the OMCD of Brattleboro rats and a mild reduction in response to dDAVP. The abundance of H(+)-ATPase was not affected by dDAVP. The increased SLC26A7 expression directly correlated with enhanced aquaporin-2 expression, which is proportional to increased interstitial osmolarity in the medulla. In conclusion, vasopressin increases the expression of SLC26A7 protein through posttranscriptional mechanisms in the OMCD. The induction of SLC26A7 by vasopressin in OMCD cells of Brattleboro rats is likely an attempt by cells to regulate their cell volume and maintain HCO(3)(-) absorption in a state associated with increased interstitial medullary tonicity.