[Effect of propranolol on dialysate myoglobin levels evoked by ischemia/reperfusion]

Although propranolol is well known to induce the preventive effect against ischemic disease, its effect on ischemia/reperfusion injuries remains unknown. We examined whether propranolol provides cardioprotection against ischemia/reperfusion injuries.

Microdialysis and 30 min of coronary artery occlusion followed by 60 min of reperfusion were applied in anesthetized rats. The dialysate myoglobin levels served as indices of myocardial injury, and were measured in the following groups: without propranolol administration (vehicle); with propranolol (2 mg x kg(-1), pro(2)-pre), (5 mg x kg(-1), pro (5) -pre) administration; zatebradine (0.5 mg x kg(-1), zat-pre) administration. Drugs were administered before coronary occlusion.

In the pro(2)-pre, pro(5)-pre and zat-pre groups the heart rate was suppressed during the entire period. Ischemia-induced increase in dialysate myoglobin level was suppressed in the pro(2)-pre, pro(5)-pre and zat-pre groups in comparison with vehicle group. Reperfusion-induced increase in dialysate myoglobin level was suppressed in the pro(2)-pre, pro(5)-pre and zat-pre groups in comparison with vehicle group. The ratios of reperfusion/ischemia myoglobin level in pro (2)-pre and pro(5)-pre were lower than those in vehicle and zat-pre. Reperfusion-induced increase in myoglobin level was suppressed by administration of propranolol immediately before reperfusion.

The results suggest that propranolol provides myocardial protection against ischemia/reperfusion injury. The protective effect of propranolol on reperfusion might be independent of its effect on ischemia.