ABSTRACT
Objective To observe the delayed cardioprotective effect of the extract of Gingkgo biloba leaves(EGb761)and its possible mechanisms in rats.Methods Myocardial ischemia-reperfusion(I/R)injury was induced by 30 min of global ischemia and 30 min of reperfusion in isolated rat hearts.Heart rate(HR),coronary flow(CF),left ventricular pressure(LVP),and its first derivatives(+dp/dtmax)were recorded,and the releasing content of creatine kinase(CK),contents of malondialdehyde(MDA)and nitric oxide(NO)in myocardial tissues were measured.Results Single ig EGb761(50 or 100 mg/kg)at 24 h before I/R were done could significantly attenuate the damage of cardiac function(LVP and +dp/dtmax)and the lowering of NO level in myocardial tissues,and inhibit the increasing in CK release and MDA level induced by I/R in myocardial tissues.The delayed cardioprotective effects of EGb761 were markedly inhibited by pretreatment with L-NAME(5 mg/kg),an inhibitor of NO synthase,or HMR1883(3 mg/kg),an antagonist of sarcolemmal ATP-sensitive potassium channels(sarcKATP).Conclusion Pretreatment with EGb761 could protect against I/R-induced myocardial injury in rats,and the delayed cardioprotection of EGb761 may be related to increasing in NO production and opening of sarcKATP.