Cell volume regulation in rat thin ascending limb of Henle's loop.
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.
Onuchic
L F
LF
Department of Physiology, Faculdade de Medicina, Universidade de São Paulo, Brazil.
Arenstein
I R
IR
Lopes
A G
AG
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003470:Culture Media; D004533:Egtazic Acid / Q000494:pharmacology; D005942:Gluconates / Q000494:pharmacology; D008138:Loop of Henle / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D009994:Osmolar Concentration; D009995:Osmosis; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D000873:Anthracenes; D002712:Chlorides; D003470:Culture Media; D005942:Gluconates; D001464:Barium; D004533:Egtazic Acid; C010030:9-anthroic acid; C030691:gluconic acid; D011188:Potassium