Stimulation of choleresis by insulin-like growth factor-I in rats

Insulin-like growth factor-I (IGF-I) is an endogenous growth factor which is mainly produced in the liver. The functions of IGF-I can be summarized as growth-promoting and insulin-like metabolic actions. In the present study, the effect of IGF-I on bile flow and bile acid secretion was investigated in rats. In normal rats bile flow was significantly increased by single exogenous administration of IGF-I, and by 1 week treatment of IGF-I, both bile flow and bile acid secretion were significantly increased. Moreover, to further understand the relationship between IGF-I and bile acid secretion, hypophysectomized rats were next used. We found that the decreases in bile flow and bile acid secretion observed in rats after hypophysectomy, as well as the decrease in the endogenous level of IGF-I in the blood, were partially reversed by 1 week exogenous IGF-I treatment. Overall, this study showed that IGF-I stimulates choleresis associated with an elevation of bile acid secretion in both normal and hypophysectomized rats when exogenously administered, suggesting the importance of IGF-I in the stimulation of choleresis in vivo.