| Objective: To investigate whether diazoxide preconditioning can trigger a cardioprotection in immature rabbits and the protective effects were compared with ischemic preconditioning and explore the role of mitochondrial KATP channels involved in PC.Methods: Thirty-four rabbits of 3-4 weeks old were divided randomly to five groups. Group I (control group, n-8); group II (diazoxide preconditioning group, n=8): After perfused with Krebs-Henseleit buffer(KHB) for 15min, the hearts were pretreated with diazoxide (100 mol/L) for 5min followed by 10min wash out with KHB; groupIII (diazoxide+5-HD preconditioning group, n=5): the hearts were pretreated with diazoxide (100 mol/L) and 5-HD (100 mol/L) ; group IV (IPC group, n=8): The hearts were preconditioned by 5min of ischemia followed by lOmin of reperfusion; group V(IPC+5-HD group, n=5):The hearts were perfused with 5-HD for 5min before IPC. The Langendorff perfusion system were built and ischemia were maintained at 38 for 30min followed by 45min reperfusion. After reperfusion, the change of hemodynamics, the CK, LDH, AST in coronary sirnus veneous effluent and the tissue ATP were measured.Myocardial ultrastructure was examined and mitochondria were assessed semi- quantitatively.Results: After reperfusion, mitochondria score of diazoxide group was lower than IPC group (P<0.01) . when added with 5-HD, the diazoxide group still has a lower score than control group (P<0.05) .LVDP, dp/dtmax, recovery had a significant improvement in group II and IV. The leakaged myocardial enzyme were the least in these two groups, which also had a higher level of tissue ATP than control group (P<0.01) .Conclusions: Diazoxide preconditioning can provide a similar protection to the hearts of immature rabbits as IPC, and protect the mitochondria better than IPC. The mKATp channels and the sKATP channels are all involved in IPC, and the mKATp channel plays a significant role.
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