[Mepindolol reduction of the degradation of phospholipids and the necrosis induced by myocardial ischemia].

Mepindolol is a newly developed beta-adrenergic blocking agent, which differs from other available beta-blockers in its ability to counteract the chronotropic effect of catecholamines without depressing myocardial contractility. This study was designed to assess whether mepindolol administration is effective in reducing infarct size. Accordingly, 53 rats were randomly assigned to 3 groups: group 1 (n = 16) underwent coronary artery occlusion without receiving any treatment, and was used as control; group 2 (n = 19) was treated with mepindolol (1 mg/kg s.c.) 5 min and every 8 hours after occlusion, for 48 hours; group 3 (n = 18) underwent a sham-operation. No difference in mortality was found among groups. The animals were sacrificed 48 hours after occlusion and the left ventricle homogenized and centrifuged. Infarct size was calculated from the residual creatine phosphokinase activity, and found to average 52.4 +/- 7.8% (mean +/- SEM) of the left ventricle in control rats and 35.6 +/- 5.4% in treated rats (p less than 0.05), indicating a 32.1% reduction of infarct size. The phospholipid content of the supernatants was also measured: it averaged 0.08 microgram P/mg of protein in sham-operated rats and 0.61 + 0.04 micrograms P/mg of protein in control animals, showing that coronary ligation induced a degradation of myocardial phospholipids. Mepindolol-treated rats, however, showed a phospholipid concentration of 0.70 +/- 0.04 microgram P/mg of protein (p less than 0.05), suggesting that the drug was able to prevent ischemia-induced phospholipase activation.(ABSTRACT TRUNCATED AT 250 WORDS)