Effects of pretreatment with nerve growth factor-beta on ischemia-reperfusion injury in isolated rat hearts:a comparison with preconditioning

Abstract

Objective To evaluate the effect of pretreatment with nerve growth factor-beta (NGF-β) on ischemia-reperfusion (I/R) injury in isolated rat hearts by comparing it with NGF-β preconditioning.Methods Pathogen-free male Sprague-Dawley rats,weighing 200-300 g,aged 8-10 weeks,were anesthetized with intraperitoneal 10％ chloral hydrate 300 mg/kg.Their hearts were excised and perfused in a Langendorff apparatus with KH solution aerated with 95％ O2 and 5％ CO2 at 37℃.Twenty-four isolated rat hearts were randomly divided into 3 groups (n =8 each) using a random number table:I/R group,NGF-β pretreatment group (group NGFPt) and NGF-β preconditioning group (group NGFPc).The hearts were perfused with K-H solution for 10 min (equilibration) in each group.In group I/R,the hearts were continuously perfused with K-H solution for 30 min.The hearts were continuously perfused with K-H solution containing NGF 0.1 μg/ml for 20 min before ischemia in group NGF-Pt.The hearts were continuously perfused with K-H solution containing NGF 0.1 μg/ml for 20 min followed by 10 min washout before ischemia in group NGFPc.The perfusion was suspended for 30 min followed by 120 min of reperfusion with K-H solution in each group.HR,left ventricular end-diastolic pressure (LVEDP),left ventricular developed pressure (LVDP) and + dp/dtmax were measured at the end of 10 min equilibration (baseline,T1),immediately before suspension of perfusion (T2),and at 5,30,60 and 120 min of reperfusion (T3-6).The activities of creatine kinase isoenzyme-MB (CK-MB) and lactate dehydrogenase (LDH) in coronary effluent were measured at T1 and T3-6.Myocardial specimens were obtained at T6 for detection of myocardial apoptosis (by TUNEL) and for microscopic examination.Apoptotic index (AI) was calculated.Results Compared with the baseline value at T1,+ dp/dtmax was significantly decreased,and LVEDP and activities of CK-MB and LDH were increased at T3-6 in each group,LVDP and HR were decreased at T3-6 in group I/R,LVDP was decreased at T3,4 in group NGFPt and at T3-6 in group NGFPc,and HR was increased at T2-6 in NGFPt and NGF Pc groups (P ＜ 0.05).Compared with group I/R,LVDP,+ dp/dtmax and HR were significantly increased and LVEDP and activities of CK-MB and LDH and AI were decreased in NGFPt and NGFPc groups (P ＜ 0.05).Compared with group NGFPc,LVDP,+ dp/dtmax and HR were significantly increased,while the LDH activity and AI were decreased (P ＜ 0.05) and no significant changes were found in LVEDP and CK-MB activity in group NGFPt (P ＞ 0.05).The pathologic changes of myocardium were significantly reduced in NGFPt and NGFPc groups as compared with I/R group.Conclusion Pretreatment with 0.1 μg/ml NGF-β attenuates I/R injury in isloated rat hearts,and the efficacy is superior to that of NGF-β preconditioning. Key words: Nerve growth factor; Ischemic preconditioning; Myocardial reperfusion injury; Pretreatment