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 µM propranolol), 30 µM 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 -adrenoceptor antagonist. Isoproterenol (30 µM) increased the late outward potassium current and net transient outward current. It is concluded that, in human atrial myocytes, -adrenergic activation reduces depolarization-activated transient and late outward potassium current and inwardly rectifying background potassium current. -Adrenergic activation resulted in an increase in the depolarization-activated transient and late outward potassium current.