Cell swelling activates basolateral membrane Cl and K conductances in rabbit proximal tubule

1990 ◽  
Vol 258 (4) ◽  
pp. F951-F962 ◽  
Author(s):  
P. A. Welling ◽  
R. G. O'Neil
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Volume Regulation ◽  
Basolateral Membrane ◽  
Cell Swelling ◽  
Base Line ◽  
Bicarbonate Buffer ◽  
Bathing Medium ◽  
Absolute Increase ◽  
Cl Conductance

The ionic basis of volume regulation was assessed in the nonperfused rabbit proximal tubule (S2 segment) by use of simultaneous measurements of tubule volume via video-optical imaging techniques and basolateral membrane voltage (Vbl) and relative ionic conductance via conventional microelectrodes. Both cell volume (9.9 +/- 0.70 nl/cm tubule length) and Vbl (-42.8 +/- 3.6 mV) remained stable in the control isotonic Ringer solution (290 mosmol/kg). When the osmolality of the bathing medium was reduced to 150 mosmol/kg, tubules swelled 72% above base line within 1 min and subsequently regulated over the course of the next 4-6 min to a steady state 20 +/- 3% above the initial base-line volume. Cell swelling was accompanied by a transient hyperpolarization of Vbl of -14.3 +/- 2.0 mV (HCO3-containing Ringer) and -10.0 +/- 0.7 mV (HCO3-free Ringer). Although the hyperpolarization was not inhibited by barium in the presence of bicarbonate buffer, addition of 2 mM Ba to a bicarbonate-free Ringer depolarized Vbl by +22 mV and abolished both the relative potassium conductance and the hyperpolarization accompanying cell swelling (delta Vbl = -4.6 +/- 0.6 mV). Furthermore, the relative conductance of K at the basolateral membrane increased from 0.16 in the isotonic control medium to 0.34 at the peak of cell swelling. Because the hyperpolarization of Vbl ensued after cells had swollen approximately 10% above base line, a modest threshold volume and time delay may be involved in triggering the volume-dependent activation of the K conductance. In parallel studies, the change in Vbl on a rapid step-change in bath Cl (49 to 4.9 mM) averaged 5.3 +/- 1.0 mV in the isotonic solution and increased to +11.3 +/- 2.1 (P less than or equal to 0.05) at the peak of cell swelling. This represented an increase in the relative Cl conductance of 0.08 to 0.20, which could only be attributed to an absolute increase in the basolateral membrane Cl conductance and not to a reduction in the other major basolateral membrane conductances. It is concluded that cell swelling results in an increase in both Cl and K conductance, which may underlie subsequent cell volume regulation.

Potassium-induced cell swelling in Necturus gallbladder epithelium

1988 ◽  
Vol 254 (5) ◽  
pp. C643-C650 ◽  
Author(s):  
C. W. Davis ◽  
A. L. Finn
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Basolateral Membrane ◽  
Cell Volume Regulation ◽  
Cell Swelling ◽  
Gallbladder Epithelium ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Per Se ◽  
Cl Conductance

In Necturus gallbladder epithelium, elevation of mucosal K+ to 95 mM in the presence of 10 mM Na+ resulted in cell swelling at a rate of 3.2% original volume per minute, followed by volume-regulatory shrinking. When Na+ was completely removed from or when amiloride (10(-4) M) was added to the mucosal medium, K+-induced cell swelling was abolished. In the presence of 10 mM Na+, 1 mM Ba2+ abolished and substitution of mucosal Cl- by NO-3 had no effect on K+-induced swelling. Thus solute entry following elevation of mucosal K+ is effected by separate K+ and Cl- pathways. Furthermore, substitution of 95 mM K+ for Na+ in the mucosal bathing medium leads to the development of a Cl- conductance in the basolateral membrane as long as some Na+ remains in the medium. However, cell swelling induced by mucosal dilution does not lead to the appearance of a Cl- conductance. Thus the activation of this conductance requires both swelling and membrane depolarization. These results show that 1) high mucosal K+ leads to cell swelling due to the entry of Cl- along with K+ and the Cl- can enter across either membrane, 2) the Cl- pathways require the presence of mucosal Na+, and 3) cell volume regulation is activated by an increase in volume per se, i.e., a hyposmotic exposure is not required for volume regulation to occur.

scholarly journals Interactions of sodium transport, cell volume, and calcium in frog urinary bladder.

1987 ◽  
Vol 89 (5) ◽  
pp. 687-702 ◽  
Author(s):  
C W Davis ◽  
A L Finn
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Cell Volume Regulation ◽  
Positive Control ◽  
Negative Control ◽  
Cell Swelling ◽  
Ionophore A23187 ◽  
Intracellular Ca

The volume of individual cells in intact frog urinary bladders was determined by quantitative microscopy and changes in volume were used to monitor the movement of solute across the basolateral membrane. When exposed to a serosal hyposmotic solution, the cells swell as expected for an osmometer, but then regulate their volume back to near control in a process that involves the loss of KCl. We show here that volume regulation is abolished by Ba++, which suggests that KCl movements are mediated by conductive channels for both ions. Volume regulation is also inhibited by removing Ca++ from the serosal perfusate, which suggests that the channels are activated by this cation. Previously, amiloride was observed to inhibit volume regulation: in this study, amiloride-inhibited, hyposmotically swollen cells lost volume when the Ca++ ionophore A23187 was added to Ca++-replete media. We attempted to effect volume changes under isosmotic conditions by suddenly inhibiting Na+ entry across the apical membrane with amiloride, or Na+ exit across the basolateral membrane with ouabain. Neither of these Na+ transport inhibitors produced the expected results. Amiloride, instead of causing a decrease in cell volume, had no effect, and ouabain, instead of causing cell swelling, caused cell shrinkage. However, increasing cell Ca++ with A23187, in both the absence and presence of amiloride, caused cells to lose volume, and Ca++-free Ringer's solution (serosal perfusate only) caused ouabain-blocked cells to swell. Finally, again under isosmotic conditions, removal of Na+ from the serosal perfusate caused a loss of volume from cells exposed to amiloride. These results strongly suggest that intracellular Ca++ mediates cell volume regulation by exerting a negative control on apical membrane Na+ permeability and a positive control on basolateral membrane K+ permeability. They also are compatible with the existence of a basolateral Na+/Ca++ exchanger.

Effects of P-glycoprotein on cell volume regulation in mouse proximal tubule

2001 ◽  
Vol 280 (5) ◽  
pp. F829-F837 ◽  
Author(s):  
Yukio Miyata ◽  
Yasushi Asano ◽  
Shigeaki Muto
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Volume Regulation ◽  
Control Volume ◽  
Regulatory Volume Decrease ◽  
Cell Volume Regulation ◽  
Hyperosmotic Stress ◽  
Cell Swelling ◽  
Bathing Solution ◽  
P Glycoprotein

The role of P-glycoprotein (P-gp) in cell volume regulation was examined in isolated nonperfused proximal tubule S2 segments from wild-type (WT) mice and those in which both mdr1a and mdr1b genes were knocked out (KO). When the osmolality of the bathing solution was rapidly decreased from 300 to 180 mosmol/kgH2O, the tubules from both the WT and KO mice exhibited regulatory volume decrease (RVD) by a similar magnitude after the initial cell swelling. The peritubular addition of two P-pg inhibitors (verapamil and cyclosporin A) to either group of the tubules had no effect on RVD. When the tubules from the WT mice were rapidly exposed to a hyperosmotic solution (500 mosmol/kgH2O) including 200 mM mannitol, they abruptly shrank to 82.1% of their control volume but remained in a shrunken state during the experimental period, indicating a lack of regulatory volume increase (RVI). The addition of the two P-gp inhibitors, but not the inhibitor of the renal organic cation transport system (tetraethylammonium), to the tubules from the WT mice resulted in RVI. Surprisingly, when the tubules from the KO mice were exposed to the hyperosmotic solution, they abruptly shrank to 79.9% of their control volume, and then gradually swelled to 87.7% of their control volume, showing RVI. However, exposure of the tubules from the KO mice to the hyperosmotic solution in the presence of the two P-gp inhibitors had no effect on RVI. When the tubules of the WT mice were exposed to the hyperosmotic solution including either of the two P-gp inhibitors, in the absence of peritubular Na+ or in the presence of peritubular ethylisopropylamiloride (EIPA; the specific inhibitor of Na+/H+ exchange), they did not exhibit RVI. In the tubules of the KO mice, both removing peritubular Na+and adding peritubular EIPA inhibited RVI induced by the hyperosmotic solution. We conclude that 1) in mouse proximal tubule, P-gp modulates RVI during hyperosmotic stress but not RVD during hyposmotic stress and 2) basolateral membrane Na+/H+ exchange partly contributes to the P-gp-induced modulation of RVI under hyperosmotic stress.

Dihydropyridine-sensitive cell volume regulation in proximal tubule: the calcium window

1990 ◽  
Vol 259 (6) ◽  
pp. F950-F960 ◽  
Author(s):  
N. A. McCarty ◽  
R. G. O'Neil
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Regulatory Volume Decrease ◽  
Cell Volume Regulation ◽  
Cell Swelling ◽  
Channel Blockers ◽  
Ca Channel ◽  
Hypotonic Solution ◽  
Dependent Manner ◽  
Intracellular Ca

The mechanism underlying the activation of hypotonic cell volume regulation was studied in rabbit proximal straight tubule (PST). When isolated non-perfused tubules were exposed to hypotonic solution, cells swelled rapidly and then underwent a regulatory volume decrease (RVD). The extent of regulation after swelling was highly dependent on extracellular Ca concentration ([Ca2+]o), with a half-maximal inhibition (K1/2) for [Ca2+]o of approximately 100 microM. RVD was blocked by the Ca-channel blockers verapamil, lanthanum, and the dihydropyridines (DHP) nifedipine and nitrendipine, implicating voltage-activated Ca channels in the RVD response. Using the fura-2 fluorescence-ratio technique, we observed that cell swelling caused a sustained rise in intracellular Ca ([Ca2+]i) only when [Ca2+]o was normal (1 mM) but not when [Ca2+]o was low (1-10 microM). Furthermore, external Ca was required early on during swelling to induce RVD. If RVD was initially blocked by reducing [Ca2+]o or by addition of verapamil during hypotonic swelling, volume regulation could only be restored by subsequently inducing Ca entry within the first 1 min or less of exposure to hypotonic solution. These data indicate a "calcium window" of less than 1 min, during which RVD is sensitive to Ca, and that part of the Ca-dependent mechanism responsible for achieving RVD undergoes inactivation after swelling. It is concluded that RVD in rabbit PST is modulated by Ca via a DHP-sensitive mechanism in a time-dependent manner.

Coupled NaCl entry into Necturus gallbladder epithelial cells

1982 ◽  
Vol 243 (3) ◽  
pp. C140-C145 ◽  
Author(s):  
A. C. Ericson ◽  
K. R. Spring
Keyword(s):  
Epithelial Cells ◽  
Cell Volume ◽  
Apical Membrane ◽  
Ionic Composition ◽  
Basolateral Membrane ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Bathing Solution ◽  
Parallel Operation ◽  
Solute Content

NaCl entry into Necturus maculosus gallbladder epithelial cells was studied by determination of the rate of fluid movement into the cell when the Na+-K+-ATPase was inhibited by 10(-4) M ouabain in the serosal bathing solution. The cell swelling was due to continuing entrance of NaCl into the cell across the apical membrane, which increased the solute content of the cell; the resultant rise in cell osmolality induced water flow and cell swelling. The rate of swelling was 4.3% of the cell volume per minute, equivalent to a volume flow across the apical membrane of 1.44 x 10(-6) cm/s, similar in magnitude to the normal rate of fluid absorption by the gallbladder. We determined the mechanism of NaCl entry by varying the ionic composition of the mucosal bath; when most of the mucosal Na+ or Cl- was replaced, cell volume did not increase during pump inhibition. The rate of NaCl entry was a saturable function of Na+ or Cl- in the mucosal bathing solution with K1/2 values of 26.6 mM for Na+ and 19.5 mM for Cl-. The mode of NaCl entry was probably not the parallel operation of Na+-H+ and Cl(-)-HCO-3 exchangers because of the lack of effect of bicarbonate removal or of the inhibitors amiloride and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid. NaCl entry was reversibly inhibited by bumetanide in the mucosal bathing solution. Transepithelial NaCl and water absorption is the result of the coupled, carrier-mediated movement of NaCl into the cell across the apical membrane and the active extrusion of Na+ by the Na+-K+-ATPase in the basolateral membrane.

Stretch-activated potassium channels in renal proximal tubule

1987 ◽  
Vol 253 (6) ◽  
pp. F1253-F1262 ◽  
Author(s):  
H. Sackin
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Negative Pressure ◽  
Basolateral Membrane ◽  
Cell Volume Regulation ◽  
K Channel ◽  
Proximal Tubule Cell ◽  
Stretch Activation ◽  
Membrane Stretch ◽  
Excised Patches

A short open-time potassium (K) channel that has previously been identified in the basolateral membrane of Necturus proximal tubule (17) is activated by membrane stretch. Application of between 12 and 20 cmH2O negative pressure to the patch pipette reversibly increases mean number of open basolateral K channels (NP0) by a factor of 5.3 +/- 2 in cell-attached patches (n = 4) and a factor of 13.7 +/- 5 in excised patches (n = 8). This stretch activation does not alter channel selectivity or conductance and depends on neither the direction of K current nor the orientation of the patch ("inside-out" vs. "outside-out"). The increase in NP0 occurs within seconds after applying negative pressure to the patch and is proportional to applied negative pressure. Stretch activation of the basolateral potassium channel may play an important role in proximal tubule cell volume regulation. For example, if swelling stretches the basolateral membrane, the resulting increase in NP0 could restore cell volume by loss of K (with an accompanying anion) followed by osmotic exit of water.

Volume regulation and intracellular calcium in the rabbit proximal convoluted tubule

1991 ◽  
Vol 260 (6) ◽  
pp. F861-F867 ◽  
Author(s):  
J. S. Beck ◽  
S. Breton ◽  
R. Laprade ◽  
G. Giebisch
Keyword(s):  
Intracellular Calcium ◽  
Cell Volume ◽  
Sodium Transport ◽  
Calcium Concentration ◽  
Basolateral Membrane ◽  
Potassium Conductance ◽  
Proximal Convoluted Tubule ◽  
Intracellular Calcium Concentration ◽  
Cell Swelling ◽  
Sustained Increase

The hypothesis that an increase of calcium leads to activation of calcium-activated ionic conductances during cell swelling was examined in the isolated perfused proximal convoluted tubule of the rabbit. Reduction of bath and luminal osmolality by 90 mosmol/kgH2O caused the cells to swell by 23.6 +/- 1.5% (n = 5) and intracellular calcium to rise from 227 +/- 35 to 347 +/- 60 nM (n = 6). Both these increases were transient, with volume decreasing to 5.5 +/- 1.2% above control and intracellular calcium concentration decreasing to 272 +/- 46 nM after 5-9 min. The addition of glucose and alanine to the tubule lumen to increase transcellular sodium transport caused a sustained increase in cell volume of 15.6 +/- 3.4% (n = 4). In parallel experiments, no significant increase in intracellular calcium concentration was observed. Addition of 1 microM of the calcium ionophore, ionomycin, reversibly increased intracellular calcium by 224 +/- 60 nM from a control value of 301 +/- 29 nM (n = 7) and reversibly depolarized the basolateral membrane by 3.6 +/- 0.9 mV (n = 5). However, there was no initial increase in the apparent transference number for potassium or chloride and no significant change in cell volume. We conclude from these observations that the sustained increase in basolateral potassium conductance observed when cells are swollen by hypotonicity or increased sodium transport (J. S. Beck and D. J. Potts. J. Physiol. Lond. 425: 369-378, 1990) is not due to a calcium-activated potassium conductance.

Stretch- and volume-activated channels in isolated proximal tubule cells

1992 ◽  
Vol 262 (5) ◽  
pp. F857-F870 ◽  
Author(s):  
D. Filipovic ◽  
H. Sackin
Keyword(s):  
Membrane Potential ◽  
Proximal Tubule ◽  
Cell Volume ◽  
Regulatory Volume Decrease ◽  
Cell Swelling ◽  
Isolated Cells ◽  
Open Probability ◽  
Proximal Tubule Cells ◽  
Open Time ◽  
Tubule Cells

Apical and basolateral channels were studied in isolated proximal tubule cells of Necturus kidney. Many of these isolated cells maintained their polarity, with clearly delineated apical and basolateral regions. A 20-pS stretch-activated (SA) cation-selective channel was identified at the apical side of these cells. This channel was permeable to Ca, K, and Na but was not significantly gated by either membrane potential or cytosolic Ca. Negative pipette pressure (15 cmH2O) increased the open probability (Po) of this channel from 0.04 +/- 0.02 to 0.26 +/- 0.08 (n = 6). Two types of Ca-independent, mechanosensitive, K-selective (SAK) channels were identified at the basolateral surface of polarized proximal tubule cells, i.e., a 30-pS long-open time (50 +/- 7 ms) channel (n = 9), and a 46-pS short-open time (1.3 +/- 0.7 ms) channel (n = 10). Pipette suction (-12 cmH2O) increased the Po of the short-open time channels from 0.008 to 0.015 and increased the Po of the long-open time channel from 0.03 to 0.19. The effect of swelling was studied with isolated cells suspended at the tip of patch pipettes. A 50% dilution of the bath doubled cell volume, hyperpolarized the membrane potential by 11 +/- 0.7 mV, and increased the Po of the basolateral SAK channels. This was followed by a spontaneous regulatory volume decrease (RVD), repolarization of the membrane potential, and a decrease in Po. In contrast, isosmotic (bath side) replacement of an impermeant anion (methanesulfonate) with a permeant anion (Cl) doubled cell volume in 5 min but without a subsequent RVD. This sustained swelling hyperpolarized the cell potential by 5.5 +/- 0.7 mV (n = 16) and increased the Po of short-open time channel by a factor of 2.3 from 0.03 +/- 0.01 to 0.07 +/- 0.02 (n = 6). The increase in Po was primarily produced by a reduction in the interburst closed time, which decreased from 142 +/- 43 ms in K methanesulfonate to 36 +/- 11 ms in KCl solutions. These results are consistent with the hypothesis that cell swelling activates Ca-independent K channels at the basolateral membrane of renal proximal tubule. Efflux of K through these channels may partially mediate renal cell volume regulation.

scholarly journals Cellular electrolyte and volume changes induced by acidosis in the rabbit proximal straight tubule.

1991 ◽  
Vol 2 (5) ◽  
pp. 1030-1040
Author(s):  
L P Sullivan ◽  
D P Wallace ◽  
R L Clancy ◽  
C Lechene ◽  
J J Grantham
Keyword(s):  
Cell Volume ◽  
Ph Effect ◽  
Basolateral Membrane ◽  
Control Level ◽  
Cell Swelling ◽  
High Pco2 ◽  
Cell Content ◽  
Cell Ph ◽  
Additional Cell ◽  
Altered Cell

Cellular acidosis induced either by high Pco2 or by low HCO3- concentrations has been shown to cause cell swelling in isolated, lumen-collapsed, S2 segments of the rabbit proximal tubule (Sullivan et al., Am J Physiol 1990; 258: F831-F839). The swelling is not followed by a volume regulatory response. The ionic basis of the swelling has been investigated by measurement of the cellular K+, Na+, and Cl- content (electron probe) and HCO3- concentration (pH-sensitive fluorescent dye). Cell content of K+, Na+, and Cl- was expressed as a ratio to P content. Exposure to 15% CO2 increased K/P from 0.98 to 1.16, Cl/P from 0.14 to 0.20, and Na/P from 0.09 to 0.11. Cell (HCO3-) increased from 22 to 32 mM. Reduction in bath (HCO3-) from 25 to 5 mM reduced cell (HCO3-) from 24 to 8 mM and increased K/P from 0.75 to 0.90. Na/P fell from 0.13 to 0.09, and Cl/P fell from 0.15 to 0.12. Thus, swelling resulting from acidosis induced by high CO2 was accompanied by an accumulation of K+, Cl-, and HCO3-; that resulting from acidosis induced by a fall in (HCO3-) was combined with an accumulation of K+ and an unidentified anion. To determine if the swelling induced by a fall in pH might be coupled with depolarization of the basolateral membrane, the effect of 1 mM barium was tested. Barium caused cell volume to increase 10.2%. Cell pH rose from 7.38 to 7.56, K/P increased from 0.63 to 0.73, Na/P did not change, and Cl/P rose from 0.17 to 0.20. Cell (HCO3-) increased 10.4 mM. When the pH of the barium-treated tissue was reduced to 7.02 by raising Pco2, additional cell swelling and accumulation of K+ occurred. The effect on cell volume of a reduction of bath (HCO3-) from 25 to 5 mM at constant bath pH was determined. Cell pH was not altered. Cell volume decreased 3% initially and then returned to the control level. When the bath (HCO3-) was restored to 25 mM, cell volume increased 3.9% and then returned to the baseline. Thus, volume regulation was not impaired. It was concluded that a fall in cell pH induces swelling, and this is coupled with an accumulation of K+. This is probably the result of a pH effect on barium-sensitive and barium-insensitive K+ conductance pathways. The nature of the anions that balance the gain in K+ depends on the means used to induce acidosis.

Cell volume regulation in rat thin ascending limb of Henle's loop

1992 ◽  
Vol 263 (3) ◽  
pp. F353-F362
Author(s):  
L. F. Onuchic ◽  
I. R. Arenstein ◽  
A. G. Lopes
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Osmotic Shock ◽  
Basolateral Membrane ◽  
Cell Volume Regulation ◽  
Tetraacetic Acid ◽  
Volume Regulatory Decrease ◽  
Henle's Loop ◽  
Volume Regulatory Increase

Thin ascending limb cells of Henle's loop from Wistar rats were studied with in vitro microperfusion and video-optical techniques to investigate their ability in regulating cell volume during osmotic shock and to identify mechanisms of ion transport involved in the process. These cells showed a clear volume regulatory decrease (VRD) response in hyposmotic medium, but no volume regulatory increase in hyperosmotic medium. The presence of barium in the bath abolished VRD. Removal of K+ from bath and perfusate also inhibited the VRD response. Reintroduction of K+ in hyposmotic conditions reestablished cell volume regulation. Introduction of anthracene-9-COOH to the basolateral medium blocked cell volume regulatory response. Cl- removal from perfusate and bath solutions also inhibited VRD, probably because of a significant intracellular Cl- depletion. Exposure of cells to ethylene glycol-bis(beta-aminoethyl ether)-N,N,N'N'-tetraacetic acid in perfusate and bath solutions reduced significantly Ca2+ concentration and impaired VRD. Reintroduction of Ca2+ in hyposmotic conditions restored volume regulation. The presence of ouabain in basolateral medium also inhibited VRD. These data suggest that the following mechanisms in the basolateral membrane are involved in VRD response: K+ and Cl- conductive pathways, which might be Ca2+ dependent for activation, and an Na(+)-K(+)-adenosinetriphosphatase.

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