Reduction of myocardial infarct size in rats under the effect of bepridil

The ability of intravenous or oral bepridil to reduce infarct size was studied in the rat submitted in situ to coronary-artery ligation. Infarct size was measured by planimetry of serial 8-micron sections at known intervals 48 hr after left-coronary-artery ligation. Succinate dehydrogenase activity (nitroblue tetrazolium stain) was used as an index of tissue viability. Bepridil was administered either intravenously (5 mg/kg) 15 min before (pretreatment) or 10 min after (post-ligation treatment) coronary-artery ligation, or orally (50 mg/kg per day) for 8 days before coronary ligation. Intravenous bepridil pretreatment reduced infarct size by more than 30%. This reduction was accompanied by a better preservation of the myocardial content of adenine nucleotides and a reduction in lactate accumulation. Intravenous post-ligation treatment and chronic oral treatment induced a reduction in infarct size similar to the one observed with intravenous preligation treatment. Thus, bepridil is equipotent in reducing infarct size whether the drug is administered intravenously before or after coronary-artery occlusion, or orally before coronary occlusion.