Regulatory volume decrease in a renal distal tubular cell line (A6). I. Role of K+ and Cl-.
Changes in volume of A6 epithelial cells were monitored by recording cell thickness (Tc). The response of Tc to a reduction of the basolateral osmolality from 260 to 140 mosmol/kg was recorded while transepithelial Na+ transport was inhibited by 20 microM amiloride. With Cl--containing bathing media, this osmotic challenge elicited a rapid rise in Tc followed by a regulatory volume decrease (RVD). Substitution of SO4(2-) or gluconate for Cl- markedly reduced the RVD, whereas cells completely maintained their ability to regulate their volume after replacing Cl- by NO3(-). A conductive pathway for Cl- excretion is suggested, which is insensitive to NPPB [5-nitro-2-(3-phenylpropylamino)benzoic acid], an inhibitor of some types of Cl- channels. Ba2+ (5 or 20 mM) reduced the RVD. A more pronounced inhibition of the RVD was obtained with 500 microM quinine, a potent blocker of volume-activated K+ channels. K+-induced depolarization of the basolateral membranes of tissues incubated with SO4(2-)-containing solutions completely abolished the RVD. Noise analysis in the presence of Ba2+ showed the activation of an apical K+ conductive pathway. These results demonstrate that cell volume regulation is controlled by processes involving Cl- and K+ excretion through conductive pathways.
De Smet
P
P
Laboratory of Physiology, K. U. Leuven, Campus Gasthuisberg, B-3000 Leuven, Belgium.
Simaels
J
J
Van Driessche
W
W
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002712:Chlorides / Q000502:physiology*; D007686:Kidney Tubules, Distal / Q000166:cytology* / Q000187:drug effects; D009579:Nitrobenzoates / Q000494:pharmacology; D009994:Osmolar Concentration; D011188:Potassium / Q000502:physiology*; D026902:Potassium Channel Blockers; D011803:Quinine / Q000494:pharmacology; D014982:Xenopus laevis
D018118:Chloride Channels; D002712:Chlorides; D009579:Nitrobenzoates; D026902:Potassium Channel Blockers; D001464:Barium; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D011803:Quinine; D011188:Potassium