ENDOTHELIN-1 STIMULATES BILE-ACID SECRETION AND VESICULAR TRANSPORT IN THE ISOLATED-PERFUSED RAT-LIVER

The effects of endothelin (ET) on portal pressure and bile secretion were examined using isolated perfused rat liver and rat hepatocyte preparations. ET-1 raised pol tal pressure dose dependently; administration at a high dose (10(-9) mol) induced a > 200% increase along with reduced bile flow and decreased secretion of bile acid and phospholipids. However, a low dose (10(-10) mol) of ET-1 brought about a < 100% portal pressure rise, enhanced both bile flow and excretion of bile acid and phospholipids, and significantly increased transfer of preadministered horseradish peroxidase (HRP) into bile. In addition, values for Ca2+ concentrations, examined by indo 1 fluorescence, were elevated in isolated hepatocytes after administration of ET-1. Papaverine suppressed the low-dose ET-1 stimulation effects on both portal pressure and bile secretion. Moreover, it also reduced the HRP excretion and suppressed intracellular Ca2+ release. This study demonstrated that ET-1 stimulates vesicular transport, probably via promotion of intracellular Ca2+ release, and, as a result, increases bile acid-dependent bile flow.