Augmentation of the Delayed Rectifier Potassium Current by ET_A Endothelin Receptor in Guinea Pig Atrial Myocytes

Abstract

The role of ET_A endothelin receptor (ET_AR) in the regulation of the delayed rectifier potassium current (I_K) was examined in guinea pig atrial myocytes. Application of ET-1 (10 nM) together with an ET_B-receptor-selective antagonist, BQ-788 (300 nM), significantly increased the voltage-dependent activation of I_K without affecting its half-activation voltage or the slope factor, while it suppressed the calcium current (I_CaL) and displaced the time-independent background current to the outward direction. The data suggests that the augmentation of I_K contributes to the ET_A-receptor-mediated shortening of action potential duration, and hence to the negative inotropic response, in atria.