Oxygen free radicals and protective effect of captopril on myocardial infarct size.

Captopril (0.25 mg/kg and 0.5 mg/kg, p.o.) decreased the myocardial infarct size and prevented the progressive decrease in voltage of the R wave in rats. It had no marked effect on systolic blood pressure at these dose levels but higher doses (1 mg/kg, p.o.) reduced systolic blood pressure. It also produced a concentration-dependent (50-700 ng/10(6) cells) decrease of chemiluminescence response from rat neutrophils and markedly reduced serum malonyldialdehyde levels, elevated as a consequence of left coronary artery ligation. It is suggested that the protective effect of captopril may be mediated through a decreased formation or scavenging of reactive oxygen species.