The Effect of pH on Na-Ca Exchange In Atrial Myocytes of Rabbit

Abstract

In atrial trabeculae and single atrial cells, we examined the effect of pH on the Na-Ca exchange mechanism. In atrial trabeculae both acidic and alkaline pH reduced Na-free contracture. Inward current of Na-Ca exchange activated by repolarizing pulse after a brief depolarizing pulse to +40 mV for 2 ms from the holding potential of -70 mV in single atrial cells was reduced by acidic pH, and enhanced by alkaline pH. Amiloride, which causes intracellular acidosis, reduced Na-Ca exchange current and 20 mM NH4CI {intracellular alkalosis}-enhanced Na-Ca exchange current. From the above results, it was concluded that the effect of pH on forward and reverse modes of Na-Ca exchange might not be symmetric.