The Protective Effect of Ischemic Preconditioning Against Hepatic Ischemic/Reperfusion Injury Under Isoflurane Anesthesia in Rats

Abstract

Introduction: Apoptosis is a central mechanism of ischemic/reperfusion (I/R) injury in the liver. Ischemic preconditioning (IP) has been shown to confer protection against I/R injury in various organs. Therefore, the aim of this study was to determine if application of IP would confer protection against hepatic I/R injury under isoflurane anesthesia in rats and investigate underlying protective mechanism. Materials and methods: Twenty-three rats weighing 270-300 g were enrolled in this study. The rats were randomly divided into three groups: (1) Sham group (n=5): sham operated group; (2) Non-IP group (n=9): 45 minutes of hepatic ischemia followed by 2 hours of reperfusion; (3) IP group (n=9): ischemic preconditioning induced by 10 minutes of hepatic ischemia followed by 15 minutes of reperfusion prior to 45 minutes of prolonged hepatic ischemia. Isoflurane (1.5%) was maintained throughout the study period (from induction to 2 h after reperfusion when animals were sacrificed). The degree of hepatic injury and the expressions of Bcl-2 and caspase 3 and 8 mRNA were compared. Results: IP group showed significantly lower levels of AST (227 ± 188 vs. 562 ± 244 U/L, P < 0.05) and ALT (136 ± 145 vs. 344 ± 178 U/L, P < 0.05) and reduction in histological grade of hepatocyte injury (Table 1) compared with Non_IP group at 2 h after reperfusion.Table: [Histologic Liver Changes at 2 h after Reperfusion]At the corresponding time, the Bcl-2 mRNA level was significantly higher (two-fold, P < 0.05) in the IP group compared to the Non_IP group (Figure 1).[Figure 1. Bcl-2 mRNA expressions]Caspase 3 mRNA level was highest in Non_IP group with statistical significance between Non_IP group and sham group. Similarly, caspase 8 mRNA level was highest in Non_IP group but no statistical significance was observed among the groups (Figure 2).[Figure 2. Caspases 3 & 8 mRNA]Conclusions: Ischemic preconditioning protected against hepatic ischemic/reperfusion injury under isoflurane anesthesia in rats. The mechanism of protection appears to occur through up-regulation of Bcl-2 expression resulting in inhibition of apoptosis.