The Protective Effect Of Naloxone On Anoxic Cardiomyocyte

Backround and Objective: It has been reported that Naloxone may provide protective effect on ischemia/reperfusion injured myocardium. But the report about the effect on apoptosis of ischemia injured cardiomyocytes and inflammatory factors has not been found. The purpose of this study is to investigate the effect of Naloxone on mitochondrial membrane potential ( m) and apotosis in hypoxia/reoxygenation cardiomyocyte and on inflammatory factors in ischemia/reperfusion cardiac tissue.Method: The study includes tow parts. Part one: second cultures of cardiomyocytes from neonate rabbits were divided into three groups: control group, hypoxia group and therapy group(hypoxia/reoxygenatio -n combined with Naloxone therapy ) and the tow latter were further divided into three subgroups: hypoxia 2h, hypoxia2h/reoxygenation 2h, hypoxia2h/reoxygen 4h. At the end of intervention, the AYm and apoptosis of cardiamyocytes were detected by flow cytometry. One another subgroup of hypoxia 2h/reoxygenation 16h was identified as DNA fragmentation by TUNEL. Part tow: the neutrophil chemoattractants IL-8, 6-Keto-Prostaglandin F/la(6-Keto-PGFla) and Thromboxane B/2(TXB2) generated in a model of myocardial infarction in 22 anesthetized male New Zealand white rabbits were investigated. The rabbits were divided into three groups randomly: sham-operation group(n=6), ischemia/reperfusion group(n=8) and therapy group (ischemia/ reperfusion combined with Naloxoneintravenous therapy, n=8). Coronary left anterior descend artery was occluded for 1 hour and reperfused for 4.5 hours. IL-8 from blood serum and ischemic tissue, 6-Keto-PGF 1 a/TXB2 from blood serum were detected using radioimmunoassays.Result: 1.After hypoxia, the m of hypoxia and therapy group were lower than that of the control(P 0.01).The AYm of therapy group was significantly higher than that of hypoxia group(P^ 0.01). 2. A remarkable losing of AYm in hypoxia group occurred during the first 2 hours of rexoygenation, while in therapy group it was occurred during the second 2h. 3.After reoxygenation for 4h or 16h, The percentage of apoptosis of hypoxia group was significantly higher than the control group and therapy group(P<0.01, respectively), There was no significant difference between therapy group and control group. The same condition was observed in the ratio of necrosis. 4.Within hypoxia group, the percentage of apoptosis was obviously higher than the percentage of necrosis(P<0.05). 5. In rabbits, the ratio of 6-Keto-PGFla/TXB2 were much lower than that of therapy group (P<0.01), while concentration of IL-8(whatever of tissue or serum) and TXB2 of ischemia/reperfusion group was obviously higher than that in the therapy group(P<0.01).Conclusion: 1 .Hypoxia/reoxygenation may cause the collapse of mitochondrial membrane potential which further led to cell's apoptosis as well as necrosis in cultured myocardial cell. Apoptosis is the major style of cell death. 2. The losing of m occurred during reoxygenation period, but not hypoxia. 3.Naloxone may significantly delay the lossing of m and then decrease the apoptosis as well as necrosis. 4. Naloxone may decrease the concentration of inflammatory factors in ischemic myocardium.