Preischemic and postischemic treatment with a new Na+/H+-exchange inhibitor, FR183998, shows cardioprotective effects in rats with cardiac ischemia and reperfusion

This study describes the pharmacologic profile of a new Na+/H(+)-exchange inhibitor, FR183998, in anesthetized rats. FR183998 had a potent inhibitory effect on Na+/H+ exchange of rat lymphocytes with median inhibitory (IC50) value of 0.3 nM. Treatment with FR183998 (0.01-0.32 mg/kg, i.v.) reduced or completely abolished ventricular fibrillation and mortality induced by 5-min ischemia followed by reperfusion, when it was administered not only 5 min before ischemia but also 1 min before reperfusion. Myocardial infarct size induced by 30-min ischemia and 60-min reperfusion was reduced significantly in a dose-dependent manner by FR183998 (0.1-1.0 mg/kg, i.v.) when the drug was administered preischemically or at an early phase of ischemia. The ventricular tachycardia and the ventricular fibrillation observed during the ischemic period also were suppressed significantly. These results indicate that FR183998 has a strong inhibitory effect on Na+/H+ exchange and suggest that treatment with FR183998 either before or immediately after the onset of ischemia can prevent the occurrence of arrhythmias and myocardial cell necrosis in situations of ischemia and reperfusion.