Endothelin-1 induces contraction of bile canaliculi in isolated rat hepatocytes

To examine the effects of endothelin-1(ET-1) on bile canalicular contractions, rat hepatocytes were isolated by a collagenase perfusion technique and cultured on p-n-p-vinylbenzenyl-D-lactonamide-coated dishes under serum-free conditions. The frequency of bile canalicular contractions was expressed by the percentage of the number of bile canaliculi(BC) that contracted compared to the total number of BC observed for 10 min. The treatment of the hepatocytes with ET-1 increased the frequency of contraction of the BC in a dose-dependent manner up to 2nM, control: 10.4%; 0.5nM ET-1:31.6%; 1nM ET-1:54.0%; 2nM ET-1:58.0%; 4nM ET-1:58.9%. The contraction, once it occurred, lasted for rest of the observation period. We also observed a transient increase in the concentration of intracellular Ca in cultured hepatocytes upon the addition of ET-1 to the medium. These results suggest that ET-1 plays an important role in the mortility of BC in vivo.