Characterization of a swelling-induced chloride conductance in cultured rat epididymal cells.
Swelling-induced Cl- conductance in cultured rat epididymal cells was characterized using whole cell patch-clamp techniques. Activation of whole cell current with an outwardly rectifying current-potential relationship was observed in cells exposed to hyposmotic solutions. This current was determined, from the observed current-reversal potentials at different Cl- concentrations, to be Cl- selective. The anion selectivity sequence of the swelling-induced Cl- conductance was I- approximately NO3- approximately Br- > Cl- > 2-(N-morpholino)ethanesulfonic acid. The swelling-induced Cl- conductance was reversibly inhibited by different Cl- channel blockers. Unlike diphenylamine-2-carboxylate or 5-nitro-2-(3-phenylpropylamino)-benzoate, which showed voltage-independent blockade, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid showed a marked voltage-dependent blockade of the volume-sensitive Cl- current, with a greater effect at depolarizing voltages. The swelling-induced Cl- conductance appeared to be different from the Ca(2+)- or adenosine 3',5'-cyclic monophosphate-activated Cl- conductances on the basis of the following observations: 1) swelling-induced current activation was seen even in the presence of kinase inhibitor (H-8) or absence of external free Ca2+, and 2) further increase in current activation could be produced by swelling after Ca(2+)- or adenosine 3',5'-cyclic monophosphate-induced current activation. The swelling-induced Cl- conductance may be involved in regulating epithelial cell volume as well as serving other important epididymal functions such as facilitating transepithelial secretion of organic compounds.
Chan
H C
HC
Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, New Territories.
Fu
W O
WO
Chung
Y W
YW
Huang
S J
SJ
Zhou
T S
TS
Wong
P Y
PY
D000818:Animals; D000838:Anions / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D002712:Chlorides / Q000037:antagonists & inhibitors / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D004553:Electric Conductivity; D004594:Electrophysiology; D004822:Epididymis / Q000166:cytology / Q000502:physiology*; D007473:Ion Channels / Q000037:antagonists & inhibitors; D008297:Male; D051381:Rats
D000838:Anions; D002712:Chlorides; D007473:Ion Channels; D000242:Cyclic AMP; D002118:Calcium