The effects of ischemic preconditioning on the injury of ischemia/reperfusion in immature rabbit hearts

Objective To study the effects of ischemic preconditioning (IPC) on the injury of ischemia/reperfusionb of isolated immature rabbit hearts and explore the possible mechanism of cardioprotection on Langendorff model. Methods After 20 min perfusion with 37 ℃ K-H perfusate, the immature hearts isolated from 3 to 4-week-old rabbits were randomly divided into IPC and control (Con) groups. The IPC group were then sub-divided into IPC1, IPC2 and IPC3 groups according to the number of IPC performed before ischemia. The hearts in IPC1, IPC2 and IPC3 groups were pretreated with 1, 2 and 3 cycles of 5min ischemia plus 5min reperfusion respectively before ischemia; but the hearts in Con group were perfused for 50 min before ischemia without IPC. All hearts under went 45 min ischemia period and 30 min reperfusion at 37 ℃. The hemodynamic indexes LVDP, LVEDP, ±dp/dt max and heart rate (HR), were recorded after 20 min of equilibration, before ischemia, and after 0, 3, 5, 10, 20 and 30 min of reperfusion. The content of ATP, SOD and MDA of myocardium was measured. Results The recovery rates of LVDP,+dp/dt max and -dp/dt max were higher in IPC 1, and IPC 2 groups than in the control (P0.05). The +dp/dt max value was higher in IPC 2 than in IPC 3 (P0.05). The value of LVEDP in IPC 1 and IPC 2 was lower than in control. The myocardial ATP content could be well maintained at higher level, by IPC,which was best seen in IPC 2, group. In IPC 2 the MDA content of myocardium was much lower than in other groups. Conclusion IPC could protect the immature myocardium from the injuries of ischemia/reperfusion, which may be attributed to the maintenance of myocardial ATP content and the depression of lipid peroaidation in the heart.