Abstract: Objective To investigate the direct effects of ischemia/ reperfusion on Na⁺/Ca²⁺ exchange current in mouse cardiac myocyte and the mechanism of [Ca²⁺] overload induced by ischemia/reperfusion.Methods The electrogenic Na⁺/Ca²⁺ exchanger currents was recorded from freshly isolated mouse ventricular myocyte during ischemia/reperfusion using nystatin-perforated patch clamp techniques.Myocardial ischemia was simulated by perfusion of metabolic inhibitor(5 mmol/L NaCN and 10 mmol/L deoxyglucose in glucose-free solution) and reperfusion was achieved by washing out the metabolic inhibitor.Results Ischemia significantly inhibited inward and outward Na⁺/Ca²⁺ exchanger currents(from(-0.04±0.01)nA to 0 nA at-100 mV; from(0.25±0.08)nA to(0.11±0.03)nA at +50 mV),Subsequent reperfusion enhanced NCX current obviously,especially the outward currents(from(0.25±0.08)nA to(0.49±0.12)nA at +50 mV).Conclusion The results suggest that ischemia/reperfusion result in significantly functional changes of Na⁺/Ca²⁺ exchanger which maybe mainly responsible for the [Ca²⁺] overload during ischemia/reperfusion.

Key words: Na⁺/Ca²⁺ exchange current, ischemia/reperfusion, ventricular myocyte, patch clamp