SEA0400, a novel Na+/Ca2+ exchanger inhibitor, reduces calcium overload induced by ischemia and reperfusion in mouse ventricular myocytes

Given the potential clinical benefit of inhibiting Na+/Ca2+ exchanger (NCX) activity during myocardial ischemia reperfusion (I/R), pharmacological approaches have been pursued to both inhibit and clarify the importance of this exchanger. SEA0400 was reported to have a potent NCX selectivity. Thus, we examined the effect of SEA0400 on NCX currents and I/R induced intracellular Ca2+ overload in mouse ventricular myocytes using patch clamp techniques and fluorescence measurements. Ischemia significantly inhibited inward and outward NCX current (from -0.04 +/- 0.01nA to 0 nA at -100 mV; from 0.23 +/- 0.08 nA to 0.11 +/- 0.03 nA at +50 mV, n=7), Subsequent reperfusion not only restored the current rapidly but enhanced the current amplitude obviously, especially the outward currents (from 0.23 +/- 0.08 nA to 0.49 +/- 0.12 nA at +50 mV, n=7). [Ca2+](i), expressed as the ratio of Fura-2 fluorescence intensity, increased to 138 +/- 7 % (P < 0.01) during ischemia and to 210 +/- 11 % (P < 0.01) after reperfusion. The change of NCX current and the increase of [Ca2+](i) during I/R can be blocked by SEA0400 in a dose-dependent manner with an EC50 value of 31 nM and 28 nM for the inward and outward NCX current, respectively. The results suggested that SEA0400 is a potent NCX inhibitor, which can protect mouse cardiac myocytes from Ca2+ overload during I/R injuries.