Role of mitochondrion-dependent apoptosis in reduction of bupivacaine-induced cardiotoxicity by lipid emulsion in rats

Objective To evaluate the role of mitochondrion-dependent apoptosis in reduction of bupivacaine-induced cardiotoxicity by lipid emulsion in rats. Methods Forty-five healthy adult male Sprague-Dawley rats, weighing 300-350 g, were divided into 3 groups by a random number table method: sham operation group (Sham group, n=5), bupivacaine group (B group, n=20), and lipid emulsion group (L group, n=20). Cardiac arrest was induced by intravenously injecting 0.4% bupivacaine 30 mg/kg over 20 s to establish the cardiotoxicity model.Twenty percent lipid emulsion was intravenously injected in a dose of 5 ml/kg during resuscitation in group L, and normal saline was intravenously injected in a loading dose of 5 ml/kg during resuscitation in group B, followed by a 3-min infusion of 1 ml·kg-1·min-1in two groups.The successful resuscitation and survival rate at 120 min of return of spontaneous circulation (ROSC) were recorded.Systolic blood pressure, heart rate, mean arterial pressure, rate-pressure product (RPP) and ratio of RPP at each time point after recovery of spontaneous heart beat to baseline value (RPPh) were recorded every 10 min after ROSC.The time from administration to cardiac arrest (T0), time from beginning of cardiopulmonary resuscitation to appearance of the first spontaneous heart beat (Ts) and time from beginning of cardiopulmonary resuscitation to appearance of ROSC (Tr) were recorded.Rats were sacrificed at 120 min of ROSC, and left ventricular tissues were obtained for determination of the expression of Bax, Bcl-2, cleaved caspase-9, cleaved caspase-3, cytochrome C (Cyt c) in cytoplasm and mitochondria (by Western blot) and expression of Bax and Bcl-2 mRNA (by real-time polymerase chain reaction) and for examination of myocardial ultrastructure. Results Compared with Sham group, the expression of Bcl-2 protein and mRNA and mitochondrial Cyt c was significantly down-regulated, and the expression of Bax protein and mRNA, cleaved caspase-9, cleaved caspase-3 and cytoplasmic Cyt c was up-regulated in B group (P 0.05), and the pathological changes of myocardium were significantly attenuated in L group. Conclusion The mechanism by which lipid emulsion reduces bupivacaine-induced cardiotoxicity may be related to inhibiting mitochondrion-dependent apoptosis in rats. Key words: Fat emulsions, intravenous; Bupivacaine; Drug-related side effects and adverse reactions; Mitochondria; Apoptosis