Role of cytoskeleton in isotonic cell volume control of rabbit proximal tubules

Stability of mammalian cell volume depends primarily on the sodium pump. When active cation transport of rabbit renal proximal tubules is blocked by ouabain, cells swell, but their size is limited by residual volume control mechanisms. This “ouabain-resistant” volume control is not an active process, as it operates in the presence of cyanide and dinitrophenol and in the absence of exogenous energy. Nevertheless, it remains incompletely explained by known transmembrane oncotic and hydrostatic forces. We tested the hypothesis that the cytoskeleton contributes to isotonic cell volume control. Isolated, collapsed rabbit proximal convoluted tubules (PCT) were crimped at both ends with micropipettes and had their volume assessed optically. PCT in ouabain (1 mM) swelled to 1.40 above control with protein, 1.62 without protein, and 1.89 with the cytoskeleton inhibitors vincristine (5 microM) and cytochalasin B (50 microM) and without protein. Tubulozole-C and cytochalasin D gave similar results. A hydrostatic pressure of 50 cmH2O increased tubule volume to 1.93 before the tubule basement membrane (TBM) prevented further volume increase. We conclude that volume of renal tubule cells in ouabain is limited partly by external protein, but primarily by the cytoskeleton. The TBM prevents massive swelling and tubule disaggregation.

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Cell volume control in Paramecium: factors that activate the control mechanisms

Journal of Experimental Biology ◽

10.1242/jeb.01417 ◽

2005 ◽

Vol 208 (3) ◽

pp. 523-537 ◽

Cited By ~ 5

Author(s):

M. Iwamoto

Keyword(s):

Cell Volume ◽

Volume Control ◽

Control Mechanisms ◽

Cell Volume Control

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Role of TASK2 Potassium Channels Regarding Volume Regulation in Primary Cultures of Mouse Proximal Tubules

The Journal of General Physiology ◽

10.1085/jgp.200308820 ◽

2003 ◽

Vol 122 (2) ◽

pp. 177-190 ◽

Cited By ~ 71

Author(s):

Herve Barriere ◽

Radia Belfodil ◽

Isabelle Rubera ◽

Michel Tauc ◽

Florian Lesage ◽

...

Keyword(s):

Cell Volume ◽

Volume Regulation ◽

Primary Cultures ◽

Regulatory Volume Decrease ◽

Cell Volume Regulation ◽

Proximal Tubules ◽

Wild Type ◽

Convoluted Tubules ◽

K Currents

Several papers reported the role of TASK2 channels in cell volume regulation and regulatory volume decrease (RVD). To check the possibility that the TASK2 channel modulates the RVD process in kidney, we performed primary cultures of proximal convoluted tubules (PCT) and distal convoluted tubules (DCT) from wild-type and TASK2 knockout (KO) mice. In KO mice, the TASK2 coding sequence was in part replaced by the lac-Z gene. This allows for the precise localization of TASK2 in kidney sections using β-galactosidase staining. TASK2 was only localized in PCT cells. K+ currents were analyzed by the whole-cell clamp technique with 125 mM K-gluconate in the pipette and 140 mM Na-gluconate in the bath. In PCT cells from wild-type mice, hypotonicity induced swelling-activated K+ currents insensitive to 1 mM tetraethylammonium, 10 nM charybdotoxin, and 10 μM 293B, but blocked by 500 μM quinidine and 10 μM clofilium. These currents were increased in alkaline pH and decreased in acidic pH. In PCT cells from TASK2 KO, swelling-activated K+ currents were completely impaired. In conclusion, the TASK2 channel is expressed in kidney proximal cells and could be the swelling-activated K+ channel responsible for the cell volume regulation process during osmolyte absorptions in the proximal tubules.

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Role of amino acids in cell volume control in the ribbed mussel: alanine and proline metabolism

10.31274/rtd-180813-5699 ◽

1981 ◽

Author(s):

Dale Edward Greenwalt

Keyword(s):

Amino Acids ◽

Cell Volume ◽

Volume Control ◽

Proline Metabolism ◽

Cell Volume Control ◽

Ribbed Mussel

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Cell volume control in vestibular dark cells during and after a hyposmotic challenge

AJP Cell Physiology ◽

10.1152/ajpcell.1994.266.4.c1046 ◽

1994 ◽

Vol 266 (4) ◽

pp. C1046-C1060 ◽

Cited By ~ 19

Author(s):

P. Wangemann ◽

N. Shiga

Keyword(s):

Cell Volume ◽

Volume Control ◽

Cell Width ◽

Volume Increase ◽

Regulatory Volume Increase ◽

Dark Cells ◽

Cell Height ◽

Vestibular Dark Cells ◽

Cell Volume Control

Cell height was measured as an index of volume in a preparation of vestibular dark cells in which the perfusate had access to both sides of the epithelium. In response to a hyposmotic challenge induced by removal of 75 mM NaCl, cell height increased to 107%; however, cell width did not increase. Significantly larger increases in cell height were observed in the absence of Cl- or K+ or in the presence of ouabain, lidocaine, barium, or quinidine, at 7 degrees C, or after fixation with glutaraldehyde. However, no significantly different swelling was observed during a hyposmotic challenge in the absence of Na+ or in the presence of bumetanide or ethoxyzolamide. Subsequent return to control osmolarity caused a regulatory volume increase that was dependent on Na+, Cl-, and K+, inhibited by bumetanide, ouabain, or 7 degrees C, however not inhibited by ethoxyzolamide, barium, quinidine, or lidocaine. The data suggest that cell volume control during the hyposmotic challenge involved a mechanism dependent on cytosolic KCl and the Na(+)-K(+)-ATPase and that the Na(+)-Cl(-)-K+ cotransporter was involved in regulatory volume increase.

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Role of cytoskeleton in volume regulation of rabbit proximal tubule in dilute medium

AJP Renal Physiology ◽

10.1152/ajprenal.1992.262.1.f144 ◽

1992 ◽

Vol 262 (1) ◽

pp. F144-F150 ◽

Cited By ~ 4

Author(s):

M. A. Linshaw ◽

C. A. Fogel ◽

G. P. Downey ◽

E. W. Koo ◽

A. I. Gotlieb

Keyword(s):

Proximal Tubule ◽

Volume Regulation ◽

Cytochalasin B ◽

Proximal Tubules ◽

Hypotonic Medium ◽

Microtubule Inhibitor ◽

Volume Regulatory Decrease ◽

Convoluted Tubules ◽

Dilute Medium

When proximal tubules are immersed in hypotonic medium, they quickly swell to a peak volume. In a second, slower phase, termed volume regulatory decrease (VRD), they shrink as K, anion, and water leave the cells. We investigated the role of the cytoskeleton during this biphasic hypotonic volume regulatory response. Isolated, collapsed rabbit proximal convoluted tubules (PCT) were crimped tightly between two pipettes, and their volume was assessed optically. PCT volume increased to a peak 70-80% above baseline on sudden immersion in dilute medium (150 mosmol/kgH2O). After completing VRD, control tubules had regulated their volume 73 +/- 2% back toward baseline. Tubules exposed to the microtubule inhibitor vincristine (5 microM) regulated 75 +/- 2%. Tubules exposed to the microfilament inhibitor cytochalasin B (50 microM) regulated less (57 +/- 5%), and tubules exposed to both inhibitors regulated only 39 +/- 3% (P less than 0.01 vs. control). Hypotonic VRD was unimpaired in PCT loaded with NaCl by prior exposure to ouabain but was significantly reduced by cytochalasin B. We conclude that VRD is not cation specific and that intact microtubules and microfilaments play a synergistic role in the VRD of rabbit PCT in hyposmotic medium.

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