Dual effect of cicletanine on the Na+-H+ exchanger in chick embryonic cardiomyocytes

Na+-H+ exchanger is thought to play an important role in the regulation of the intracellular pH (pH(i)) and in the cardiac cell injury induced by isch emia and reperfusion. The aim of this study was to assess the effect of cic letanine, an antihypertensive compound in humans, which has been reported t o have cardioprotective effect under an ischemia-reperfusion process, on Na +-H+ exchanger activity in ventricular cardiomyocytes isolated from chick e mbryo. Na+-H+ exchanger activity was assessed by the rate of pH(i) recovery after an acid load. A dual effect was observed: at low concentration of ci cletanine (10(-7) M), Na+-H+ exchanger activity was significantly decreased , whereas at higher concentrations (10(-6)-10(-5) M), a significant stimula tion of the exchanger was observed. These results suggest that cicletanine modulates pH(i) recovery in cardiac cells after cellular acid load.