CHLORIDE CONDUCTANCE IN HUMAN ATRIAL CELLS

Many types of chloride current have been reported in the hearts of var ious 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 atria l cells using the whole-cell voltage-clamp method, External applicatio n of 1 mu M 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 betwee n -80 and +50 mV. Neither external application of 10 mu M forskolin no r internal application of 50 mu M cyclic AMP activated a cyclic AMP-de pendent chloride current. On the other hand, when the same cell was su perfused 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 = 1 0), 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 wa s observed in human atrial cells. On the other hand, a swelling-induce d chloride current was consistently demonstrated and its kinetic prope rties were similar to those reported in other cardiac myocytes. (C) 19 95 Academic Press Limited (C) 1995 Academic Press Limited