Randall Packer | The George Washington University (original) (raw)

Papers by Randall Packer

ABSTRACT Vita. Thesis--Pennsylvania State University. Includes bibliographical references (leaves... more ABSTRACT Vita. Thesis--Pennsylvania State University. Includes bibliographical references (leaves 54-57). Photocopy of typescript.

Tiwari, Swasti, Randall K. Packer, Xinqun Hu, Yoshihisa Sugimura, Joseph G. Verbalis, and Carolyn... more Tiwari, Swasti, Randall K. Packer, Xinqun Hu, Yoshihisa Sugimura, Joseph G. Verbalis, and Carolyn A. Ecelbarger. Increased renal -ENaC and NCC abundance and elevated blood pressure are independent of hyperaldosteronism in vasopressin escape. Am J Physiol Renal Physiol 291: F49–F57, 2006. First published January 31, 2006; doi:10.1152/ajprenal.00390.2005.—Previously, we demonstrated that rats undergoing vasopressin escape had increased mean arterial blood pressure (MAP), plasma and urine aldosterone, and increased renal protein abundance of the -subunit of the epithelial sodium channel (ENaC), the thiazide-sensitive Na-Cl cotransporter (NCC), and the 70-kDa band of -ENaC (Song J, Hu X, Khan O, Tian Y, Verbalis JG, and Ecelbarger CA. Am J Physiol Renal Physiol 287: F1076–F1083, 2004; Ecelbarger CA, Knepper MA, and Verbalis JG. J Am Soc Nephrol 12: 207–217, 2001). Here, we determine whether changes in these renal proteins and MAP require elevated aldosterone levels. We performed adrenal...

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Na+/H+ exchangers (NHE) mediate at least part of Na+ entry into gill epithelia via Na+/NH4+ excha... more Na+/H+ exchangers (NHE) mediate at least part of Na+ entry into gill epithelia via Na+/NH4+ exchange. For homeostasis, Na+ entry into and exit via Na+/K+ ATPase from gill epithelia must balance. Na+/K+ ATPase activity is reduced in cold- compared to warm-acclimated freshwater temperate fish. We hypothesized gill NHE activity is greater in warm- than cold-acclimated fish when measured at acclimation temperatures, and NHE activity displays a temperature dependence similar to Na+/K+ ATPase. Since NHE mRNA expression does not differ, we measured the Na+-dependence of pH-induced Na+ fluxes in gill vesicles from warm- and cold-acclimated fathead minnows at 20o and 7 °C, and calculated maximum transport rates (Vmax) and Na+ K1/2s. We also measured NH4+-induced Na+ fluxes and Na+-induced H+ fluxes. In vesicles from warm-acclimated fish, NHE Vmaxs were 278 ± 33 and 149 ± 23 arbitrary unit/s (au/s) and Na+ K1/2s were 12 ± 4 and 6 ± 4 mmol/l when assayed at 20o and 7 °C (p < 0.004), respectively. In vesicles from cold-acclimated fish, Vmaxs were 288 ± 35 and 141 ± 13 au/s and Na+ K1/2s 17 ± 5 and 7 ± 2 mmol/l when assayed at 20o and 7 °C (p < 0.002), respectively. Na+-induced H+ fluxes were 98 ± 8 and 104 ± 26 au/s in warm- and cold-acclimated fish assayed at 20 °C, respectively. Na+/NH4+ exchange was 120 ± 11 and 158 ± 13 au/s in warm- and cold-acclimated fish, respectively. Conclusions: Gill NHE activity was greater in warm- than cold-acclimated fish assayed at acclimation temperatures. The temperature dependence of NHE activity was similar in both groups, but differed from that reported for Na+/K+ ATPase suggesting complex mechanisms to maintain Na+ homeostasis.

American Journal of Physiology-Renal Physiology

To investigate whether the enhancement of thick ascending limb (TAL) NaCl transport in response t... more To investigate whether the enhancement of thick ascending limb (TAL) NaCl transport in response to long-term increases in circulating vasopressin concentration is associated with increased expression levels of the apical Na-K-2Cl cotransporter in the rat TAL, we have carried out immunoblotting and immunofluorescence studies using affinity-purified, peptide-directed antibodies. Semiquantitative immunoblotting studies demonstrated a marked increase (193% of controls) in Na-K-2Cl cotransporter band density in response to restriction of water intake to 15 ml/day for 7 days. In contrast, the expression levels of two other apical proteins of the TAL (the type 3 Na/H exchanger and Tamm-Horsfall protein) were unchanged in the outer medulla. A 7-day subcutaneous infusion of the V2receptor-selective vasopressin analog, 1-desamino-[8-d-arginine]vasopressin (DDAVP), to Brattleboro rats also markedly increased Na-K-2Cl cotransporter expression in the outer medulla (183% of controls). Immunofluor...

American Journal of Physiology-Renal Physiology

Increased systemic acid intake is associated with an increase in apical Na/H exchange in the rena... more Increased systemic acid intake is associated with an increase in apical Na/H exchange in the renal proximal tubule mediated by the type 3 Na/H exchanger (NHE3). Because NHE3 mediates both proton secretion and Na absorption, increased NHE3 activity could inappropriately perturb Na balance unless there are compensatory changes in Na handling. In this study, we use semiquantitative immunoblotting of rat kidneys to investigate whether acid loading is associated with compensatory decreases in the abundance of renal tubule Na transporters other than NHE3. Long-term (i.e., 7-day) acid loading with NH4Cl produced large decreases in the abundances of the thiazide-sensitive Na-Cl cotransporter (TSC/NCC) of the distal convoluted tubule and both the β- and γ-subunits of the amiloride-sensitive epithelial Na channel (ENaC) of the collecting duct. In addition, the renal cortical abundance of the proximal type 2 Na-dependent phosphate transporter (NaPi-2) was markedly decreased. In contrast, abund...

Journal of the American Society of Nephrology

Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ... more Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ammonium accumulation mediated by active NH 4 ϩ absorption by the medullary thick ascending limb. To investigate whether alterations in the abundance of medullary thick ascending limb ion transporters, namely the apical Na ϩ /K ϩ (NH 4 ϩ)/2Cl Ϫ-cotransporter (BSC-1), the apical Na ϩ /H ϩ-exchanger (NHE3), and the Na ϩ /K ϩ-ATPase ␣1-subunit, may be responsible in part for altered medullary ammonium accumulation, semiquantitative immunoblotting studies were performed using homogenates from the inner stripe of the rat renal outer medulla. After 7 d of NH 4 Cl (7.2 mmol/220 g body wt per d) loading (associated with increased medullary ammonium accumulation), neither BSC-1 nor Na ϩ /K ϩ-ATPase protein expression was altered, but NHE3 protein abundance was significantly increased. On

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Comparative biochemistry and physiology. Part D, Genomics & proteomics, Mar 1, 2018

In the face of ongoing climate change, it is imperative to understand better the effects of tempe... more In the face of ongoing climate change, it is imperative to understand better the effects of temperature on immune function in freshwater teleosts. It is unclear whether previously observed changes were caused by temperature per se. We studied changes in the gill transcriptome of fathead minnows (Pimephales promelas) at low temperature to understand better the effects of temperature on immune function. De novo assembly of the transcriptome using Trinity software resulted in 73,378 assembled contigs. Annotation using the Trinotate package yielded 58,952 Blastx hits (accessions). Expression of 194 unique mRNA transcripts changed in gill tissue of fathead minnows acclimatized to 5° compared to controls at 22 °C. At 5 °C mRNAs coding for proteins involved in innate immune responses were up-regulated. Those included proteins that block early-stage viral replication and macrophage activation. Expression of mRNAs coding for pro-inflammatory molecules and mucus secretion were also enhanced. ...

Journal of the American Society of Nephrology : JASN, 1997

Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from gluc... more Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from glucocorticoid binding by an enzyme, 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2). To study the role of 11 beta-HSD2 in acid-base homeostasis, 11 beta-HSD2 activity was measured in rat IMCD-enriched cell suspensions. Homogenates of cell suspensions were incubated in buffers ranging in pH from 6.00 to 8.15 in the presence of 1 microCi of 3H-corticosterone (CS) and 400 microM NAD+. Enzyme activity was expressed as the amount of 3H-CS converted to 3H-11-dehydrocorticosterone (DHCS). IMCD 11 beta-HSD2 activity at pH 6.5 was 49% of activity at pH 7.5; 22.5 versus 11.0 fmol/microgram of protein per h. Experiments also were performed on intact cell suspensions at pH 7.5 and 6.5. There was a 42% inhibition in the IMCD cell suspension conversion rate of 3H-CS to 3H-11-DHCS at pH 6.5; 13.1 versus 7.6 fmol/microgram per h (P < 0.005). In cell suspensions at pH 7.5, 1-day acid loading c...

Contributions to nephrology, 1997

... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whor... more ... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whorwood CB, Valentino R, Burt D, Sheppard MC, Edwards CRW: 11-Beta-hydroxy-steroid dehydrogenase activity and gene expression in the hypertensive Bianchi-Milan rat. ...

Journal of the American Society of Nephrology : JASN, 1995

Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organ... more Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organic anions (OA). Although citrate is the only OA previously identified as being excreted in appreciable amounts during base loading, citrate excretion accounts for only part of total OA excretion. The objectives of this study were to identify other OA excreted by rats and to see how their excretion changed in response to moderate (8 micro Eq/g per day) and heavy (30 micro Eq/g per day) loads of NaHCO3 and NH4Cl. Urinary OA were identified by high-performance liquid chromatography and were measured by enzymatic techniques as well. It was found that, in addition to citrate, significant quantities of alpha-ketoglutarate (alpha-KG) were excreted by base-loaded rats and that the excretion of citrate, alpha-KG, and succinate increased with base loading and decreased with acid loading. Citrate plus alpha-KG excretion rates were, respectively, two-thirds and one-third the rate of HCO3- excretion ...

Physiological reviews, 1989

The American journal of physiology, 1989

Bicarbonate is formed when organic anions are oxidized systemically. Therefore, changes in organi... more Bicarbonate is formed when organic anions are oxidized systemically. Therefore, changes in organic anion excretion can affect systemic acid-base balance. To assess the role of organic anions in urinary acid-base excretion, we measured urinary excretion in control rats, NaHCO3-loaded rats, and NH4Cl-loaded rats. Total organic anions were measured by the titration method of Van Slyke. As expected, NaHCO3 loading increased urine pH and decreased net acid excretion (NH4+ + titratable acid - HCO3-), whereas NH4Cl loading had the opposite effect. Organic anion excretion was increased in response to NaHCO3 loading and decreased in response to NH4Cl loading. We quantified the overall effect of organic ion plus inorganic buffer ion excretion on acid-base balance. The amounts of organic anions excreted by all animals in this study were greater than the amounts of NH4+, HCO3-, or titratable acidity excreted. In addition, in response to acid and alkali loading, changes in urinary organic anion ...

The American journal of physiology, 1989

The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed t... more The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed that water or solute fluxes across the PSE might result in changes in urine or medullary interstitial fluid composition. To study osmotic water and chloride permeabilities, the PSE was dissected from underlying medullary tissue and mounted in a small Ussing chamber. Osmotic water permeability was low (14.2 +/- 3.0 microns/s) and was unaffected by 100 nM vasopressin added to the basolateral surface. In contrast, the PSE showed a substantial chloride permeability of 3.1 +/- 0.4 x 10(-5) cm/s that decreased reversibly to 2.2 +/- 0.3 x 10(-5) cm/s (P less than 0.01) with vasopressin. Vasopressin also reversibly increased the transepithelial resistance of the PSE from 87 +/- 9 to 106 +/- 13 omega.cm2 (P less than 0.02). Apical bumetanide (10(-6) M) had no significant effect on PSE chloride permeability. The apparent Na-Cl permeability ratio (0.75 +/- 0.01) calculated from dilution potential me...

The American journal of physiology, 1990

The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the out... more The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the outer surface of the renal papilla and has an apical surface that faces the urinary space. We studied acid-base transport in this epithelium by dissecting it from the papilla, mounting it in a modified Ussing chamber, and following pH changes in the apical bathing solution. The experiments demonstrated that the PSE is capable of acidifying the apical solution at a substantial rate. The acidification rate was similar with 100% nitrogen and 100% oxygen (with and without 10 microM antimycin A), ruling out a dependence on oxidative metabolism. Addition of 1 mM iodoacetate decreased apical acidification by 55%, suggesting a dependence on glycolysis. The net rate of lactate secretion was only 17% of the total acid secretion rate, indicating that apical acidification was not directly caused by secretion of lactic acid alone. Removal of sodium or potassium from the apical solutions or the addition ...

Journal of the American Society of Nephrology : JASN, 1991

Ammonium (NH3 plus NH4+), produced predominantly in the proximal tubule, is transferred to the fi... more Ammonium (NH3 plus NH4+), produced predominantly in the proximal tubule, is transferred to the final urine by a process involving countercurrent multiplication of ammonium which generates an ammonium concentration gradient in the renal medulla. It was hypothesized that if urinary ammonium excretion rates are controlled in part by the medullary ammonium gradient, changes in hydration and acid-base state should cause changes in the medullary ammonium gradient consistent with expected changes in urinary ammonium concentrations. To test that hypothesis, rats were subjected to water diuresis, water deprivation, water deprivation plus furosemide, and dietary acid and base loads and corticomedullary ammonium gradients in their kidneys were then measured. Sections were cut along the corticomedullary axis to yield slices of cortex, outer stripe of outer medulla, inner stripe of outer medulla, and three levels of the inner medulla. The total ammonia content of homogenized slices was measured ...

Contributions to nephrology, 1991

ABSTRACT Vita. Thesis--Pennsylvania State University. Includes bibliographical references (leaves... more ABSTRACT Vita. Thesis--Pennsylvania State University. Includes bibliographical references (leaves 54-57). Photocopy of typescript.

Tiwari, Swasti, Randall K. Packer, Xinqun Hu, Yoshihisa Sugimura, Joseph G. Verbalis, and Carolyn... more Tiwari, Swasti, Randall K. Packer, Xinqun Hu, Yoshihisa Sugimura, Joseph G. Verbalis, and Carolyn A. Ecelbarger. Increased renal -ENaC and NCC abundance and elevated blood pressure are independent of hyperaldosteronism in vasopressin escape. Am J Physiol Renal Physiol 291: F49–F57, 2006. First published January 31, 2006; doi:10.1152/ajprenal.00390.2005.—Previously, we demonstrated that rats undergoing vasopressin escape had increased mean arterial blood pressure (MAP), plasma and urine aldosterone, and increased renal protein abundance of the -subunit of the epithelial sodium channel (ENaC), the thiazide-sensitive Na-Cl cotransporter (NCC), and the 70-kDa band of -ENaC (Song J, Hu X, Khan O, Tian Y, Verbalis JG, and Ecelbarger CA. Am J Physiol Renal Physiol 287: F1076–F1083, 2004; Ecelbarger CA, Knepper MA, and Verbalis JG. J Am Soc Nephrol 12: 207–217, 2001). Here, we determine whether changes in these renal proteins and MAP require elevated aldosterone levels. We performed adrenal...

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Na+/H+ exchangers (NHE) mediate at least part of Na+ entry into gill epithelia via Na+/NH4+ excha... more Na+/H+ exchangers (NHE) mediate at least part of Na+ entry into gill epithelia via Na+/NH4+ exchange. For homeostasis, Na+ entry into and exit via Na+/K+ ATPase from gill epithelia must balance. Na+/K+ ATPase activity is reduced in cold- compared to warm-acclimated freshwater temperate fish. We hypothesized gill NHE activity is greater in warm- than cold-acclimated fish when measured at acclimation temperatures, and NHE activity displays a temperature dependence similar to Na+/K+ ATPase. Since NHE mRNA expression does not differ, we measured the Na+-dependence of pH-induced Na+ fluxes in gill vesicles from warm- and cold-acclimated fathead minnows at 20o and 7 °C, and calculated maximum transport rates (Vmax) and Na+ K1/2s. We also measured NH4+-induced Na+ fluxes and Na+-induced H+ fluxes. In vesicles from warm-acclimated fish, NHE Vmaxs were 278 ± 33 and 149 ± 23 arbitrary unit/s (au/s) and Na+ K1/2s were 12 ± 4 and 6 ± 4 mmol/l when assayed at 20o and 7 °C (p < 0.004), respectively. In vesicles from cold-acclimated fish, Vmaxs were 288 ± 35 and 141 ± 13 au/s and Na+ K1/2s 17 ± 5 and 7 ± 2 mmol/l when assayed at 20o and 7 °C (p < 0.002), respectively. Na+-induced H+ fluxes were 98 ± 8 and 104 ± 26 au/s in warm- and cold-acclimated fish assayed at 20 °C, respectively. Na+/NH4+ exchange was 120 ± 11 and 158 ± 13 au/s in warm- and cold-acclimated fish, respectively. Conclusions: Gill NHE activity was greater in warm- than cold-acclimated fish assayed at acclimation temperatures. The temperature dependence of NHE activity was similar in both groups, but differed from that reported for Na+/K+ ATPase suggesting complex mechanisms to maintain Na+ homeostasis.

American Journal of Physiology-Renal Physiology

To investigate whether the enhancement of thick ascending limb (TAL) NaCl transport in response t... more To investigate whether the enhancement of thick ascending limb (TAL) NaCl transport in response to long-term increases in circulating vasopressin concentration is associated with increased expression levels of the apical Na-K-2Cl cotransporter in the rat TAL, we have carried out immunoblotting and immunofluorescence studies using affinity-purified, peptide-directed antibodies. Semiquantitative immunoblotting studies demonstrated a marked increase (193% of controls) in Na-K-2Cl cotransporter band density in response to restriction of water intake to 15 ml/day for 7 days. In contrast, the expression levels of two other apical proteins of the TAL (the type 3 Na/H exchanger and Tamm-Horsfall protein) were unchanged in the outer medulla. A 7-day subcutaneous infusion of the V2receptor-selective vasopressin analog, 1-desamino-[8-d-arginine]vasopressin (DDAVP), to Brattleboro rats also markedly increased Na-K-2Cl cotransporter expression in the outer medulla (183% of controls). Immunofluor...

American Journal of Physiology-Renal Physiology

Increased systemic acid intake is associated with an increase in apical Na/H exchange in the rena... more Increased systemic acid intake is associated with an increase in apical Na/H exchange in the renal proximal tubule mediated by the type 3 Na/H exchanger (NHE3). Because NHE3 mediates both proton secretion and Na absorption, increased NHE3 activity could inappropriately perturb Na balance unless there are compensatory changes in Na handling. In this study, we use semiquantitative immunoblotting of rat kidneys to investigate whether acid loading is associated with compensatory decreases in the abundance of renal tubule Na transporters other than NHE3. Long-term (i.e., 7-day) acid loading with NH4Cl produced large decreases in the abundances of the thiazide-sensitive Na-Cl cotransporter (TSC/NCC) of the distal convoluted tubule and both the β- and γ-subunits of the amiloride-sensitive epithelial Na channel (ENaC) of the collecting duct. In addition, the renal cortical abundance of the proximal type 2 Na-dependent phosphate transporter (NaPi-2) was markedly decreased. In contrast, abund...

Journal of the American Society of Nephrology

Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ... more Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ammonium accumulation mediated by active NH 4 ϩ absorption by the medullary thick ascending limb. To investigate whether alterations in the abundance of medullary thick ascending limb ion transporters, namely the apical Na ϩ /K ϩ (NH 4 ϩ)/2Cl Ϫ-cotransporter (BSC-1), the apical Na ϩ /H ϩ-exchanger (NHE3), and the Na ϩ /K ϩ-ATPase ␣1-subunit, may be responsible in part for altered medullary ammonium accumulation, semiquantitative immunoblotting studies were performed using homogenates from the inner stripe of the rat renal outer medulla. After 7 d of NH 4 Cl (7.2 mmol/220 g body wt per d) loading (associated with increased medullary ammonium accumulation), neither BSC-1 nor Na ϩ /K ϩ-ATPase protein expression was altered, but NHE3 protein abundance was significantly increased. On

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Comparative biochemistry and physiology. Part D, Genomics & proteomics, Mar 1, 2018

In the face of ongoing climate change, it is imperative to understand better the effects of tempe... more In the face of ongoing climate change, it is imperative to understand better the effects of temperature on immune function in freshwater teleosts. It is unclear whether previously observed changes were caused by temperature per se. We studied changes in the gill transcriptome of fathead minnows (Pimephales promelas) at low temperature to understand better the effects of temperature on immune function. De novo assembly of the transcriptome using Trinity software resulted in 73,378 assembled contigs. Annotation using the Trinotate package yielded 58,952 Blastx hits (accessions). Expression of 194 unique mRNA transcripts changed in gill tissue of fathead minnows acclimatized to 5° compared to controls at 22 °C. At 5 °C mRNAs coding for proteins involved in innate immune responses were up-regulated. Those included proteins that block early-stage viral replication and macrophage activation. Expression of mRNAs coding for pro-inflammatory molecules and mucus secretion were also enhanced. ...

Journal of the American Society of Nephrology : JASN, 1997

Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from gluc... more Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from glucocorticoid binding by an enzyme, 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2). To study the role of 11 beta-HSD2 in acid-base homeostasis, 11 beta-HSD2 activity was measured in rat IMCD-enriched cell suspensions. Homogenates of cell suspensions were incubated in buffers ranging in pH from 6.00 to 8.15 in the presence of 1 microCi of 3H-corticosterone (CS) and 400 microM NAD+. Enzyme activity was expressed as the amount of 3H-CS converted to 3H-11-dehydrocorticosterone (DHCS). IMCD 11 beta-HSD2 activity at pH 6.5 was 49% of activity at pH 7.5; 22.5 versus 11.0 fmol/microgram of protein per h. Experiments also were performed on intact cell suspensions at pH 7.5 and 6.5. There was a 42% inhibition in the IMCD cell suspension conversion rate of 3H-CS to 3H-11-DHCS at pH 6.5; 13.1 versus 7.6 fmol/microgram per h (P < 0.005). In cell suspensions at pH 7.5, 1-day acid loading c...

Contributions to nephrology, 1997

... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whor... more ... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whorwood CB, Valentino R, Burt D, Sheppard MC, Edwards CRW: 11-Beta-hydroxy-steroid dehydrogenase activity and gene expression in the hypertensive Bianchi-Milan rat. ...

Journal of the American Society of Nephrology : JASN, 1995

Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organ... more Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organic anions (OA). Although citrate is the only OA previously identified as being excreted in appreciable amounts during base loading, citrate excretion accounts for only part of total OA excretion. The objectives of this study were to identify other OA excreted by rats and to see how their excretion changed in response to moderate (8 micro Eq/g per day) and heavy (30 micro Eq/g per day) loads of NaHCO3 and NH4Cl. Urinary OA were identified by high-performance liquid chromatography and were measured by enzymatic techniques as well. It was found that, in addition to citrate, significant quantities of alpha-ketoglutarate (alpha-KG) were excreted by base-loaded rats and that the excretion of citrate, alpha-KG, and succinate increased with base loading and decreased with acid loading. Citrate plus alpha-KG excretion rates were, respectively, two-thirds and one-third the rate of HCO3- excretion ...

Physiological reviews, 1989

The American journal of physiology, 1989

Bicarbonate is formed when organic anions are oxidized systemically. Therefore, changes in organi... more Bicarbonate is formed when organic anions are oxidized systemically. Therefore, changes in organic anion excretion can affect systemic acid-base balance. To assess the role of organic anions in urinary acid-base excretion, we measured urinary excretion in control rats, NaHCO3-loaded rats, and NH4Cl-loaded rats. Total organic anions were measured by the titration method of Van Slyke. As expected, NaHCO3 loading increased urine pH and decreased net acid excretion (NH4+ + titratable acid - HCO3-), whereas NH4Cl loading had the opposite effect. Organic anion excretion was increased in response to NaHCO3 loading and decreased in response to NH4Cl loading. We quantified the overall effect of organic ion plus inorganic buffer ion excretion on acid-base balance. The amounts of organic anions excreted by all animals in this study were greater than the amounts of NH4+, HCO3-, or titratable acidity excreted. In addition, in response to acid and alkali loading, changes in urinary organic anion ...

The American journal of physiology, 1989

The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed t... more The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed that water or solute fluxes across the PSE might result in changes in urine or medullary interstitial fluid composition. To study osmotic water and chloride permeabilities, the PSE was dissected from underlying medullary tissue and mounted in a small Ussing chamber. Osmotic water permeability was low (14.2 +/- 3.0 microns/s) and was unaffected by 100 nM vasopressin added to the basolateral surface. In contrast, the PSE showed a substantial chloride permeability of 3.1 +/- 0.4 x 10(-5) cm/s that decreased reversibly to 2.2 +/- 0.3 x 10(-5) cm/s (P less than 0.01) with vasopressin. Vasopressin also reversibly increased the transepithelial resistance of the PSE from 87 +/- 9 to 106 +/- 13 omega.cm2 (P less than 0.02). Apical bumetanide (10(-6) M) had no significant effect on PSE chloride permeability. The apparent Na-Cl permeability ratio (0.75 +/- 0.01) calculated from dilution potential me...

The American journal of physiology, 1990

The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the out... more The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the outer surface of the renal papilla and has an apical surface that faces the urinary space. We studied acid-base transport in this epithelium by dissecting it from the papilla, mounting it in a modified Ussing chamber, and following pH changes in the apical bathing solution. The experiments demonstrated that the PSE is capable of acidifying the apical solution at a substantial rate. The acidification rate was similar with 100% nitrogen and 100% oxygen (with and without 10 microM antimycin A), ruling out a dependence on oxidative metabolism. Addition of 1 mM iodoacetate decreased apical acidification by 55%, suggesting a dependence on glycolysis. The net rate of lactate secretion was only 17% of the total acid secretion rate, indicating that apical acidification was not directly caused by secretion of lactic acid alone. Removal of sodium or potassium from the apical solutions or the addition ...

Journal of the American Society of Nephrology : JASN, 1991

Ammonium (NH3 plus NH4+), produced predominantly in the proximal tubule, is transferred to the fi... more Ammonium (NH3 plus NH4+), produced predominantly in the proximal tubule, is transferred to the final urine by a process involving countercurrent multiplication of ammonium which generates an ammonium concentration gradient in the renal medulla. It was hypothesized that if urinary ammonium excretion rates are controlled in part by the medullary ammonium gradient, changes in hydration and acid-base state should cause changes in the medullary ammonium gradient consistent with expected changes in urinary ammonium concentrations. To test that hypothesis, rats were subjected to water diuresis, water deprivation, water deprivation plus furosemide, and dietary acid and base loads and corticomedullary ammonium gradients in their kidneys were then measured. Sections were cut along the corticomedullary axis to yield slices of cortex, outer stripe of outer medulla, inner stripe of outer medulla, and three levels of the inner medulla. The total ammonia content of homogenized slices was measured ...

Contributions to nephrology, 1991