Transmembrane chloride currents in human atrial myocytes.
The present study was designed to evaluate the presence of basal, swelling-induced, and cAMP-dependent Cl- currents in human atrial myocytes studied with the whole cell patch-clamp technique. Under basal conditions, a small outwardly rectifying background conductance was noted that reversed close to 0 mV and was not altered by Cl- replacement. Isoproterenol (1 microM), forskolin (3 microM), and 8-bromoadenosine 3',5'-cyclic monophosphate (50 microM) did not increase membrane conductance, even when responsiveness to isoproterenol was confirmed by an increase in Ca2+ current and when perforated-patch techniques (nystatin) were used. Exposure to hyposmotic solutions increased cell volume and induced a whole cell conductance that showed outward rectification, was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (100 microM), and responded to changes in Cl- gradient in a fashion consistent with a Cl(-)-selective conductance, with estimated relative permeabilities of 1, 0.25, and 0.07 for Cl-, methanesulfonate, and aspartate, respectively. The results suggest that human atrial cells lack basal and adenosine 3',5'-cyclic monophosphate-dependent Cl- current but manifest a substantial Cl- conductance in the presence of cell swelling.
Li
G R
GR
Department of Medicine, Montreal Heart Institute, Quebec, Canada.
Feng
J
J
Wang
Z
Z
Nattel
S
S
D000818:Animals; D016275:Atrial Function; D002462:Cell Membrane / Q000502:physiology; D002712:Chlorides / Q000037:antagonists & inhibitors / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D004553:Electric Conductivity; D006168:Guinea Pigs; D006801:Humans; D008698:Mesylates / Q000494:pharmacology; D009206:Myocardium / Q000166:cytology; D009997:Osmotic Pressure
D002712:Chlorides; D008698:Mesylates; C045880:methanesulfonic acid; D000242:Cyclic AMP