Isovolumetric regulation of renal proximal tubules in hypotonic medium.
Isolated nonperfused proximal tubules maintained their cell volume at a constant level (isovolumetric regulation, IVR), when osmolality of the bathing medium was gradually decreased from 290 to 190 mosm at 1.5 and 5.0 mosm/min. Hypotonic IVR was blocked by inhibiting the Na(+)-K+ pump with ouabain (10(-4) M) when osmolality was decreased at 1.5 or 5 mosm/min. Concentration-dependent inhibition of cell volume maintenance was observed in the presence of the K+ channel blocker barium (10(-3)-10(-2) M) when osmolality decreased at 5 mosm/min. Quinine (10(-3) M), another K+ channel blocker, also inhibited IVR at osmolality decreases of 1.5 and 5 mosm/min. These results suggest that the maintenance of constant cell volume during gradual hypoosmotic exposure involves mechanisms that depend on intact Na-K-ATPase and the controlled loss of intracellular K+.
Department of Medicine, State University of New York, Buffalo.
J W
JW
Lohr
D000818:Animals; D001464:Barium / Q000494:pharmacology; D005260:Female; D007038:Hypotonic Solutions; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000502:physiology*; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011803:Quinine / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase; D014882:Water-Electrolyte Balance
D007038:Hypotonic Solutions; D015221:Potassium Channels; D001464:Barium; D010042:Ouabain; D012964:Sodium; D011803:Quinine; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium