Chloride conductance in human atrial cells.
Many types of chloride current have been reported in the hearts of various species; however, the nature of chloride conductance in the human heart is still unclear. We investigated cyclic AMP-dependent chloride current and swelling-induced chloride current in isolated human atrial cells using the whole-cell voltage-clamp method. External application of 1 microM isoprenaline increased calcium current by 391.9 +/- 48.6% (mean +/- S.D., n = 8); however, there was no activation of cyclic AMP-dependent chloride current at steady-state membrane potentials between -80 and +50 mV. Neither external application of 10 microM forskolin nor internal application of 50 microM cyclic AMP activated a cyclic AMP-dependent chloride current. On the other hand, when the same cell was superfused with a 50% hypotonic solution, it exhibited osmotic swelling and an outward rectifying current (6.59 +/- 0.96 pA/pF at +30 mV, n = 10). This swelling-induced current reversed at -26.5 +/- 3.1 mV (n = 10), close to the calculated equilibrium potential for chloride, and it was sensitive to the stilbene-derivative chloride channel blocker. In conclusion, no activation of cyclic AMP-dependent chloride current was observed in human atrial cells. On the other hand, a swelling-induced chloride current was consistently demonstrated and its kinetic properties were similar to those reported in other cardiac myocytes.
Sakai
R
R
Heart Institute of Japan, Tokyo Women's Medical College, Japan.
Hagiwara
N
N
Kasanuki
H
H
Hosoda
S
S
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000293:Adolescent; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000328:Adult; D000368:Aged; D016275:Atrial Function; D002648:Child; D002675:Child, Preschool; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006325:Heart Atria / Q000166:cytology; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007223:Infant; D015640:Ion Channel Gating / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008564:Membrane Potentials; D008875:Middle Aged; D009206:Myocardium / Q000166:cytology*; D009997:Osmotic Pressure; D018408:Patch-Clamp Techniques
D000318:Adrenergic beta-Agonists; D018118:Chloride Channels; D002712:Chlorides; D007038:Hypotonic Solutions; D005576:Colforsin; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000242:Cyclic AMP; D007545:Isoproterenol