| Objective: To explore the role and related mechanisms of melatonin during the ischemia and reperfusion injury in rat liver. Methods: With a rat model of segmental(70%) hepatic ischemia, 78 healthy male SD rats were randomized into 3 groups:(1)sham-operation group(s),n=6,the rats were underwent anesthesia, hilus dissection and media injection intraperitoneally;(2)ischemia/reperfusion group(I/R), n=36,the partial liver lobes were subject to 70min ischemia and following reperfusion of 0,1,3,6,9,12h respectively, n=6 at each time point and the liver specimens were harvested. (3)melatonin group(Mel),n=36, melatonin (10mg/kg) were administrated i.p at two occasions, 15 min before ischemia and immediately before the reperfusion period. The time point and rat number of each time point were identical with the I/R group. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were determined to assess liver functions. Liver tissues were taken for determination of glutathione (GSH) levels, activity of myeloperoxidase (MPO) and inducible Nitric Oxide synthase (iNOS);the determination of apoptotic activity was assessed by Tunel and the expression of nuclear factor-κB (NF-κB) and intercellular adhesion molecule-1(ICAM–1) were examined by immunohistochemical technique. Results: (1)Hepatocytic apoptosis index(HAI)and the expression of NF-κB: There was no expression of NF-κB and only slight amount of hepatocytic apoptosis in S group; After ischemia without reperfusion, the expression of NF-κB and hepatocyte apoptosis index in both I/R group and Mel group were no statistic significance compared with S group(p>0.05),however, the expression of NF-κB and hepatocyte apoptosis index in both I/R group and Mel group increased and reached the top at 6h and 9h time point respectively during the reperfusion period. the expression of NF-κB and hepatocyte apoptosis index in Mel group were significantly lower than I/R group at each corresponding time point during reperfusion(p<0.01). (2)The activity of MPO: There was no difference among three groups at 0 time point(P>0.05) whereas the activity of MPO in both I/R group and Mel group increased continuously and reached the top at 9h time point, the activity of MPO in Mel group was significantly lower than that in I/R group(P<0.01).(3)The expression of ICAM-1: There was no expression in S group and no difference between I/R and Mel group(P>0.05). The expression of ICAM-1 increased in both I/R and Mel groups after reperfusion and reached the top at 9h time point, The expression of ICAM-1 in Mel group was significantly lower than that in I/R group at each corresponding time point.(P<0.01).(4)Glutathione (GSH) levels: There was mild drop of GSH in both I/R and Mel groups compared with S group at 0h time point although there was no difference between the two groups(P>0.05).The GSH level decreased sharply in I/R group when reperfusion was performed and its bottom came at 9h time point. The GSH level in Mel group was significantly higher than that in I/R group at each corresponding time point(P<0.01).(5)The activity of iNOS: 0-1h after reperfusion, there was no difference among three groups(P>0.05).At eachfollowing time point, the activity of iNOS in I/R group was much higher than that of S group(P<0.01)and reached the top at 9h time point. The activity of iNOS in Mel group was significantly lower than that of I/R group at each corresponding time point after 1h(P<0.01).(6)The changes of serum aminotransferase(ALT ,AST): The aminotransferase increased significantly after reperfusion in I/R group and came its top at 9h time point then tend to drop, its level was significantly higher than that in S group (P<0.01). The aminotransferase in Mel group was lower than that in I/R group at each corresponding time point(P<0.01)except the 0h time point(P>0.05). Conclusion: Melatonin can down-regulate the expression of NF-κB during ischemia and reperfusion in rat liver, depress the activity of iNOS, lessen the infiltration of neutrophil and elevate the GSH level of liver thus depress the hepatocytic apoptosis and protect the liver from ischemia and reperfusion injury.
|
PDF Full Text Request