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Regulatory volume decrease in a renal distal tubular cell line (A6). II. Effect of Na+ transport rate
P De Smet1, J Simaels, W Van Driessche
1Laboratory of Physiology, K. U. Leuven, Campus Gasthuisberg, B-3000 Leuven, Belgium.
Pflugers Archiv : European Journal of Physiology
|October 1, 1995
Summary
Xenopus laevis kidney A6 epithelia cell volume regulation was studied. Blocking basolateral potassium channels increased cell thickness, while regulatory volume decrease depended on active transport and basolateral potassium channels.
Area of Science:
- Cell Biology
- Renal Physiology
- Epithelial Transport
Background:
- A6 epithelia from Xenopus laevis kidney are a model for studying ion and water transport.
- Understanding cell volume regulation is crucial for kidney function.
Purpose of the Study:
- To investigate the effects of inhibiting and stimulating transepithelial sodium (Na+) transport on cell volume and its regulation during osmotic challenges.
- To elucidate the role of basolateral potassium (K+) channels in cell volume regulation.
Main Methods:
- Culturing A6 epithelia on permeable supports in an Ussing-type chamber.
- Measuring cell thickness (Tc), short-circuit current (Isc), and transepithelial conductance (Gt).
- Manipulating apical and basolateral solutions, and using inhibitors like ouabain, Ba2+, and quinine.
Main Results:
- Apical osmotic reduction did not significantly alter cell volume, indicating low apical water permeability.
- Blocking active transport with ouabain increased cell thickness.
- Blocking basolateral K+ channels with Ba2+ significantly increased cell thickness.
- Regulatory volume decrease (RVD) during basolateral hypotonicity was abolished by ouabain, Ba2+, or quinine.
Conclusions:
- Cell volume regulation in A6 epithelia is tightly coupled between apical and basolateral transport processes.
- Basolateral K+ channels play a critical role in mediating RVD.
- Ouabain inhibits RVD likely due to K+ depletion, while Ba2+ and quinine inhibit it by blocking K+ efflux pathways.