Changes in iNOS expression in brain injury induced by hepatic ischemia-reperfusion in rats

Objective To investigate the changes in iNOS expression in brain injury induced by hepatic ischemia-reperfusion (IR) in rats.Methods Thirty-two male Wistar rats weighing 240-280 g were randomly divided into 2 groups: sham operation group (group S,n = 8) and group IB( n = 24).The hepatic IR was induced by clamping the hepatic artery and portal vein according te the method described by LONG et al.In group IR the rats were killed at 3,6 and 24 h of reperfusion after 40 min hepatic ischemia (8 rats at each time point).The rats in group S were also killed.The brains were removed for determination of NO content (by nitrate reductase assay),SOD activity (by xanthine oxidase method),MDA content(by colorimetric method),nitrotyrosine (NT) expression (by Western blot),and iNOS mRNA expression (by RT-PCR).Results Compared with group S,cerebral NO and MDA content were significantly increased at 6 and 24 h of reperfusion,expression of cerebral NT and iNOS mRNA up-regulated and SOD activity decreased at 6 h of reperfusion in group IR (P < 0.05 or 0.01).Cerebral NO and MDA content were significantly higher and SOD activity lower at 6 and 24 h of reperfusion than at 3 h of reperfusion in group IR (P < 0.05).Conclusion The expression of iNOS in brain tissues is up-regulated after hepatic IR and it produces a great amount of NO inducing brain injury through peroxynitrite (ONOO-). Key words: Nitric-oxide synthase; Brain injuries; Liver; Reperfusion injury