Characteristics of the inward-rectifying potassium current in mouse ventricular myocytes and its relation to early after-depolarization

摘要

The properties of the inward-rectifying potassium current (I_(K1) were studied in the single myocytes isolated from adult mouse ventricles by the whole-cell patch-clamp technique for the first time Most of the properties of I_(K1) including channel conductances, activation, inactivation, rectification and external K~+ sensitivity in mouse ventricular myocyte were similar to those in other species, but the current-voltage (I-V) curve of mouse ventricular myocyte showed no negative slope, i e the slopein the range of membrane potential 50 mV positive to the reversal potential (F_(Rev)) was virtually flat and remained at a low current level ((59±39) pA). Under the superfusion of Tyrode's solution with 3mmol/L K~+ and 3mmol/L Cs~+, I_(K1) in the aboveregion nearly decreased to zero, and then the early after-depolarization (BAD) occurred. The results suggest that this distinctive characteristic of I_(K1) in mouse ventricular myocyte may relate to the high susceptibility to BAD in mouse myocardium. The inhibition of I_(K1) seems to be a prerequisite for the occurrence of EAD in this experiment.