Fluorescence Analysis of the Mitochondrial Effect of a Plasmalemmal Na+/Ca2+ Exchanger Inhibitor, SEA0400, in Permeabilized H9c2 Cardiomyocytes

We investigated the effect on mitochondrial Ca2+ of SEA0400, an inhibitor of the Na+/Ca2+ exchanger (NCX) which reduces mitochondrial Ca2+ overload during myocardial ischemia, in digitonin-permeabilized H9c2 cells expressing the mitochondrial-targeted Ca2+ indicator, yellow cameleon 3.1. The elevation of mitochondrial Ca2+ concentration caused by an increase in extramitochondrial Ca2+ concentration was inhibited by carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP) or ruthenium red, but enhanced by CGP-37157, a mitochondrial NCX inhibitor. SEA0400 had no effect on mitochondrial Ca2+ under normal and ischemic conditions. Thus, the mitochondria-protective effects of SEA0400 could be explained by inhibition of plasmalemmal NCX but not mitochondrial NCX.