Effect of rapamycin on expression of vascular endothelial growth factor mRNA after biliary ischemia in rats

Abstract

Objective To investigate the effect of rapamycin on the expression of vascular endothelial growth factor (VEGF) mRNA after deprivation of biliary blood supply.Methods Male SD rats were randomly assigned into 4 groups:sham (n =28),sham + rapamycin (n =28),ischemia (n =32) and ischemia + rapamycin (n =32).In ischemia groups,complete deprivation of bile duct arterial supply was performed,and in sham groups,open-close operation was carried out.Daily intake of rapamycin (2 mg/kg) was given in rapamycin treated groups with the same volume of saline in non-rapamycin treated groups.Body weight was measured before operation,and on the postoperative day (POD) 7 and 14.Six rats were sacrificed on POD 1,3 and 7,and the rest on POD 14.Fresh liver tissues were obtained,followed by VEGF immunohistochemical stain and real-time polymerase chain reaction (Real-time PCR) (dye method).Kruskal-Wallis H test was used for comparison of multiple independent samples and the following pairwise comparisons were performed by rank transformation and ONE WAY ANOVA.Statistic difference was considered when P ＜ O.05.Results In ischemia group,obvious VEGF positive staining was found within portal areas,which mainly located at vascular endothelium.In sham or sham + rapamycin groups,less obvious positive staining was found right after surgey,and VEGF mRNA was increased sharply in ischemia group and reached the peak level on POD 3 (5.19 ±0.15).On POD 1,3 and 7,VEGF mRNA expression level was significantly lower in ischemia + rapamycin group than in ischemia group (P ＜ 0.05).Conclusion Rapamycin inhibits VEGF mRNA expression,which provides explanation to negative effect of rapamycin on adaptive bile duct proliferation in response to ischemia. Key words: Rapamycin; Bile duct ischemia; Vascular endothelial growth factor