Adrenergic Modulation of Potassium Currents in Isolated Human Atrial Myocytes.
The adrenergic modulation of inwardly rectifying and depolarization-activated outward potassium currents was studied in single cardiac myocytes obtained from the human atrium. Membrane currents were recorded in enzymatically dissociated cells using the whole-cell voltage-clamp technique. It was observed that, in the presence or absence of atenolol (or 1 &mgr;M propranolol), 30 &mgr;M phenylephrine attenuated inwardly rectifying and depolarization-activated outward potassium currents including both transient and late-activated current. This suppressant effect of phenylephrine could be prevented by pretreatment with an alpha-adrenoceptor antagonist. Isoproterenol (30 &mgr;M) increased the late outward potassium current and net transient outward current. It is concluded that, in human atrial myocytes, alpha-adrenergic activation reduces depolarization-activated transient and late outward potassium current and inwardly rectifying background potassium current. beta-Adrenergic activation resulted in an increase in the depolarization-activated transient and late outward potassium current. Copyright 1994 S. Karger AG, Basel
Su
M.-J.
MJ
Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
Chi
J.-F.
JF
Chu
S.-H.
SH