Abstract

The purpose of this study was to investigate the inhibitory role of vitamin A with respect to activation of Ito cells in fibrosis of the rat liver induced by common bile duct ligation(CBDL). The liver was examined by immunohistochemical staining for a-smooth muscle actin,the known marker of activated Ito cells, and light and electron microscopy after CBDL andCBDL with intraperitoneal injection of retinoic acid (Sigma, USA) 1 mg/Kg in 3 times per week. The results were sumrrlerized as follows: After CBDL, the bile ductules were markedly proliferated in the periportal areas extending toterminal hepatic veins. Interstitial fibrosis and inflammatory cell infiltration appeared, however,cholestasis was minimal. Retinoic acid treatment with CBDL decreased bile ductular proliferationand interstitial fibrosis compared to CBDL only. After CBDL, proliferated and activated Ito ceIs showing positive reaction in smooth muscle actin were present in the periductular andperisinusoidal areas, and areas of increased interstitial fibrosis. Activated ito cells weredecreased in number after CBDL with vitamin A treatment. Electron microscopically,intracytoplasmic fat droplets and the cytoplasmic processes of Ito cells were decreased afterCBDL. Myofibroblasts were frequently appeared in the interstitial fibrosis after CBDL. But,intracytoplasmic fat droplets of Ito cells were well preserved, and myofibroblasts were found lessfrequently after CBDL with vitamin A treatment. The results suggest that vitamin A plays an inbitory role in the activation and fibrogenesis ofIto cells after CBDL.

• Keywords: Liver;Fibrosis;Ito cell;Myofibroblast;Vitamin A;