Effects of diazoxide postcongditioning on the cell viability,phospho glycogen synthase kinase-3β,Bcl-2,Bax protein expressionin in cultured adult rat cardiac myocytes suffered from hypoxia/reoxygenation injury

Objective To investigate the effect of diazoxide (DZ) postconditioning mediating the expression of phospho glycogen synthase kinase-3β,Bcl-2,Bax and the cell viability during hypoxia/reoxygenation (H/R) in cultured adult rat cardiac myocytes.Methods The model of isolated adult rat cardiac myocytes was established and randomly divided into 5 groups (n=6):① Normal group:caridocytes were incubated at 37 ℃ in a humidified atmosphere of 5％ carbon dioxide CO2) and 95％ air for 6 h; ② H/R group:cardiocytes were exposed to 3 h of hypoxia followed hy 3 h of reoxygenation; ③ DZ group:cardiocytes were exposed to 3 h of hypoxia followed by 3 hof reoxygenation,while 100 μ mol/L DZ was added in medium 5 min after reoxygenation; ④ DZ+5-hydroxydecanoate(5-HD) group:cardiocytes were exposed to 3 h of hypoxia followed by 3 h of reoxygenation,while 100 μmol/L 5-HD was added in medium rightly after 3 h' hypoxia and 100 μmol/L DZ was added in medium 5 min after reoxygenation; ⑤ 5-HD group:3 h of hypoxia followed by 3 h of reoxygenation,while 100 μmol/L 5-HD was added in medium after 3 h' hypoxia.The cell viability was assayed by the rate of Rod-shaped cells; the expression of pGSK-3β,Bcl-2 and Bax were assessed by western blot 3 h after reoxygenation.Results After 3 h reoxygenation,contraction of the single myocyte is (13.12±0.19)％ in normal group.Compared with the normal group,the cell viability was gready decreased in the other 4 groups [(7.97±0.22)％ for H/R group,(10.48± 0.20)％ for DZ group,(7.97±0.19)％ for the DZ+5-HD group,(8.22±0.22)％ for the 5-HD group](P＜0.05).The cell viability in DZ group was(64±5)％.Compared with the H/R group,it was significantly increased(P＜0.05).The content of Bcl-2 and pGSK-3β in DZ group were higher(P＜0.05),while the expression of Bax was lower(P＜0.05).But these effects were abolished with administration of 5-HD rightly after hypoxia(P＞0.05); There was no statistical difference between H/R group and 5-HD group(P＞0.05).Conclusions DZ could alleviate hypoxia/reoxygenation injury through mediating the expression of pGSK-3β,Bax,Bcl-2 proteins via opening of mitoKATP channel. Key words: Diazoxide;  Postconditioning;  Mitochondrial ATP-sensitive potassium channel;  glycogen synthase kinase-3β;  Bcl-2 ;  Bax