Evidence for proteic water pathways in the luminal membrane of kidney proximal tubule (original) (raw)
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Water Permeability of Brush Border Membrane Vesicles from Kidney Proximal Tubule
Journal of Membrane Biology, 1997
Brush border membrane vesicles (BBMV) maintain an initial hydrostatic pressure difference between the intra-and extravesicular medium, which causes membrane strain and surface area expansion ). This has not been taken into account in prior osmotic water permeability P f evaluations. In this paper, we find further evidence for the pressure in the variation of stopped-flow light scattering traces with different vesicle preparations. Response to osmotic shock is used to estimate water permeability in BBMV prepared with buffers of different osmolarities (18 and 85 mosM). Data analysis includes the dissipation of both osmotic and hydrostatic pressure gradients. P f values were of the order of 4 × 10 −3 cm sec −1 independent of the osmolarity of the preparation buffer. Arrhenius plots of P f vs. 1/T were linear, showing a single activation energy of 4.6 kcal mol −1 . The initial osmotic response which is significantly retarded is correlated with the period of elevated hydrostatic pressure. We interpret this as an inhibition of P f caused by membrane strain and suggest how this inhibition may play a role in cell volume regulation in the proximal tubule.
Biology of the Cell, 1997
Brush border membrane vesicles (BBMV) from rabbit kidney proximal tubule cells, prepared with different internal solute concentrations (cellobiose buffer 13,18 or 85 mosM) developed an hydrostatic pressure difference across the membrane of 18.7 mosM, that causes a membrane tension close to 5 x 10-s N cm-l. When subjected to several hypertonic osmotic shocks an initial delay of osmotic shrinkage (a lag time), corresponding to a very small change in initial volume was apparent. This initial osmotic response, which is significantly retarded, was correlated with the initial period of elevated membrane tension, suggesting that the water permeability coefficient is inhibited by membrane stress. We speculate that this inhibition may serve to regulate cell volume in the proximal tubule. kidney vesicles / hydrostatic pressure / membrane stress / osmotic behavior
Functionally induced changes in water transport in the proximal tubule segment of rat kidneys
International journal of nephrology and renovascular disease, 2011
To eliminate freezing artifacts in the proximal tubule cells, two cryotechniques were applied to normal rat kidneys, ie, freeze substitution and special freeze drying. In addition, salt depletion and salt loading were applied to groups of rats to evaluate whether the segmental structure of the proximal tubule could be altered. In the superficial part of the renal cortex of normal kidneys, the typical first segment structure in the proximal tubule was generally present in the early postglomerular fraction of the tubule. However, in the second segment, a special cellular phenomenon was constantly present, comprising a significant intercellular space that was easily identified using a light microscope. In the third segment, in which the presence of basolateral interdigitations is minimal, the small lateral space, which was found to be present in cryopreparations between neighboring cells from the normal kidney, was found to be enlarged by heavy salt loading of short duration. It is con...
Water permeation in Madin-Darby canine kidney cells is modulated by membrane fluidity
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1991
Simultaneous determinations of water and antipytine permeatimts in monulayers of Madin-Darby canine kidney (MDCK) cells grown on a permeant support were done to study the relationships hameen water transport and membrane fluidity in these epithelial calls. The changes in permeation of the lipophilie non-electrulyte antipyrirm were used to probe the modifications in membrane fluidity, in controls, the apparent diffusional permeability coefficient [or water (PDw) was three times higher than the annpyrlne's one, Poap (4.2" l0-s vs. 1.4" 10-s em s-I). Add~tlon ot vasopressin or dihutyryl cyclic AMP to the monoiayers induced a hiphasie incense in antlpyrlne permeation with peak values at t = 2 mln, 3-4-fold that of conlruls. Variations in water permeation were of similar amplitude and obeyed the same lime course, leaving the water to ontipyrlne permeztlon ratio~ unchanged. Compound H'l, an inhibitor of protein kinases, blunted the increase in permeatinn for both antipyrlne and water. Finally, addition ol tile fluidizin~ agent benzyl alcohol to the monolayers resulted in a parsllel increase in Poap and Pt~,. These results suggest that the physical state of membrane lipids may control water permeation in MDCK cells.
Characterization of the chloride conductance in porcine renal brush-border membrane vesicles
Pfl�gers Archiv European Journal of Physiology, 1998
The chloride conductance in brush-border membrane vesicles prepared from pig kidney cortex was investigated using a light-scattering assay, anion-diffusion-potential-dependent Na + -D-glucose cotransport and 36 Clinflux. K + -diffusion-potential-driven salt exit from, or entry into, the vesicles was slow in the presence of gluconate, SO 4 2and F -, intermediate with Cland Br -, and fast with I -, NO 3 -, and SCN -. Stimulation of Na + -Dglucose uptake followed a similar anion sequence. Conductive Clflux had a low activation energy and was inhibited by suphhydryl reagents, the stilbene disulphonates 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonate (SITS) and 4,4'-diisothiocyanato-2,2'-disulphonate (DIDS), and the arylaminobenzoates diphenylamine-2-carboxylic acid (DPC) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Intravesicular Ca 2+ and extravesicular nucleotides were without effect on conductive Clflux. These characteristics tentatively exclude some known Clchannels and leave members of the ClC family as possible candidates responsible for the Clconductance in brush-border membranes.
Maturational Changes in Rabbit Renal Basolateral Membrane Vesicle Osmotic Water Permeability
Journal of Membrane Biology, 2000
We have recently demonstrated that while the osmotic water permeability (P f ) of neonatal proximal tubules is higher than that of adult tubules, the P f of brushborder membrane vesicles from neonatal rabbits is lower than that of adults. The present study examined developmental changes in the water transport characteristics of proximal tubule basolateral membranes by determining aquaporin 1 (AQP1) protein abundance and the P f in neonatal (10-14 days old) and adult rabbit renal basolateral membrane vesicles (BLMV). At 25°C the P f of neonatal BLMV was significantly lower than the adult BLMV at osmotic gradients ranging from 40 to 160 mOsm/kg water. The activation energies for osmotic water movement were identical in the neonatal and adult BLMV (8.65 ± 0.47 vs. 8.86 ± 1.35 kcal и deg −1 и mol −1 ). Reflection coefficients for sodium chloride and sodium bicarbonate were identical in both the neonatal and adult BLMV and were not different from one. Mercury chloride (0.5 mM) reduced osmotic water movement by 31.3 ± 5.5% in the adult BLMV, but by only 4.0 ± 4.0% in neonatal vesicles (P < 0.01). Adult BLMV AQP1 abundance was higher than that in the neonate. These data demonstrate that neonatal BLMV have a lower P f and AQP1 protein abundance than adults and that a significantly greater fraction of water traverses the basolateral membrane lipid bilayer and not water channels in neonates compared to adults. The lower P f of the neonatal BLMV indicates that the basolateral membrane is not responsible for the higher transepithelial P f in the neonatal proximal tubule.
Biophysical Journal, 1987
Diffusional water permeability was measured in renal proximal tubule cell membranes by pulsed nuclear magnetic resonance using proton spin-lattice relaxation times (T1). A suspension of viable proximal tubules was prepared from rabbit renal cortex by Dounce homogenization and differential sieving. T1 measured in a tubule suspension (22% of exchangeable water in the intracellular compartment) containing 20 mM extracellular MnCl2 was biexponential with time constants 1.8 +/- 0.1 ms and 8.3 +/- 0.2 ms (mean +/- SD, n = 8, 37 degrees C, 10 MHz). The slower time constant, representing diffusional exchange of water between intracellular and extracellular compartments, increased to 11.6 +/- 0.6 ms (n = 6) after incubation of tubules with 5 mM parachloromercuribenzene sulfonate (pCMBS) for 60 min at 4 degrees C and was temperature dependent with activation energy Ea = 2.9 +/- 0.4 kcal/mol. To relate T1 data to cell membrane diffusional water permeabilities (Pd), a three-compartment exchange model was developed that included intrinsic decay of proton magnetization in each compartment and apical and basolateral membrane water transport. The model predicted that the slow T1 was relatively insensitive to apical membrane Pd because of low luminal/cell volume ratio. Based on this analysis, basolateral Pd (corrected for basolateral membrane surface convolutions) is 2.0 X 10(-3) cm/s, much lower than corresponding values for basolateral Pf (10-30 X 10(-3) cm/s) measured in the intact tubule and in isolated basolateral membrane vesicles. The measured P,/Pd> 1, low Ea and inhibition of Pd by pCMBS provide strong evidence that water transport in the proximal tubule basolateral membrane is facilitated by a specialized aqueous pore or narrow channel.
Effect of cystine loading and cystine dimethylester on renal brushborder membrane transport
Bioscience Reports, 1990
The effect of loading renal tubule cells with cystine was studied by incubating them with cystine dimethylester. Proline uptake into brushborder membrane vesicles isolated from the cystine loaded cells was not different from that observed into brushborder vesicles isolated from tubules incubated in buffer alone. Incubating brushborder membranes with 2 mM cystine dimethylester for 10 minutes reduced the uptake of proline by 27% after 15 seconds of incubation and by 21% after 60 seconds of incubation. There was no effect after 20 minutes of incubation. Pre-incubating brushborder membrane vesicles with cystine dimethylester had no statistically significant effect on the affinity of priline for the carrier, but did reduce the maximal rate of proline uptake by 49%.
Transport ofl-cystine by rat renal brush border membrane vesicles
Pfl�gers Archiv European Journal of Physiology, 1983
Brush border membranes were isolated from rat renal cortex by a divalent cation precipitation method. L-35Scystine uptake into the vesicles was measured by a rapid filtration method. Covalent incorporation of tracer into membrane proteins was observed after prolonged incubations. At short incubation periods (1 min) binding was small and allowed an analysis of transmembrane transport. To guarantee transport of L-cystine, the experiments were performed in the presence of the oxidant diamide.