Abstract
Objective To investigate the effects of different concentrations of nitroglycerin on ischemia-reperfusion (IR) injury in the isolated rat hearts. Methods Healthy adult male SD rats 7 weeks old weighing 220-330 g were anesthetized with intraperitoneal pentobarbital 50 mg/kg. Their hearts were excised and perfused in a Langendorff apparatus. Thirty isolated hearts were randomly divided into 3 groups (n = 10 each) : group 1R, low-concentration nitroglycerin group (group LN) and high-concentration nitroglycerin group (group HN). The hearts in group IR were perfnsed with plain modified K-H solution. The hearts in group LN were perfused with K-H solution containing nitroglycerin 2.5 μg/L. The hearts in group HN were perfnsed with K-H solution containing nitroglycerin 25 μg/L. After 15 min of post-preparation equilibration, IR was induced by 20 min suspension of perfusion followed by 60 min reperfusion. HR, left ventricular end-diastolic pressure (LVEDP), coronary flow (CF), left ventricular developed pressure (LVDP), + dp/dtmax, and - dp/dtmax were measured at 10, 20, 30, 40, 50 and 60 min of reperfusion. To determine the activities of myocardial lactate dehydrogenase (LDH) and creatine kinase (CK), 1.5 ml of coronary effluent was collected at the end of equilibration, and at 5, 30 and 60 min of reperfusion. At 60 min of reperfusion, myocardial tissues were obtained to determine myocardial infarct size (IS) (by Trc staining) and assess the apoptosis rate (by TUNAL technique) .Results Compared with group IR, HR, CF, LVDP, + dp/dtmax and - dp/dtmax were significantly increased in group LN, while significantly decreased in group HN, and LVEDP, activities of CK and LDH in the coronary effluent, myocardial IS and apoptosis rate were significantly decreased in group LN, while significantly increased in group HN (P < 0.05). Compared with group LN, HR, CF, LVDP, + dp/dtmax and - dp/dtmax were significantly decreased, and LVEDP, activities of CK and LDH in the coronary effluent, myocardial IS and apoptosis rate significantly increased in group HN (P < 0. 05). Conclusion Low-concentration nitroglycerin can attenuate myocardial IR injury in isolated rat hearts, but high-concentration nitroglycerin can exacerbate the injury. Key words: Nitroglycerin; Myocardial reperfusion injury
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