Abstract:Objective ：To investigate the direct effect of endothelin-1 on the contraction of Oddi sphincter, and study its signal transduction pathway. Methods ：By cumulative increase method, ET-1 was given in K-H solution up to the final concentration （0.1～100.0nmol/L）, and the contraction amplitude and frequency of Oddi sphincter were observed. Anti-ET serum,nicardipine, and BQ-123 were added to detect their effects on the contraction of Oddi sphincter,and PKC activity in Oddi sphincter were also detected. Results ：ET addition resulted in the contraction of resting Oddis sphincter,and the contraction intensity increased with the rising ET concentration. No obvious inhibition effect on Oddis sphincter contraction was induced by nicardipine, while anti-ET serum and ET receptor antagonist reduced the Oddi sphincter contraction significantly.The PKC activity in cytoplasm of Oddi sphincter enhanced with the rising ET-1 concentration, and the contraction of Oddis sphincter increased at the same time. Conclusions ：ET-1 results in the significant contraction of the vivo Oddi sphincter, and the magnitude of contraction is dose-effect related to ET concentration. Anti-ET serum and ET receptor antagonistsstrongly offset the function of ET. PKC is involved in the signal transduction pathway of the Oddi sphincter contraction induced by ET-1.