Endothelin-1 Induces Cholestasis Which Is Mediated by an Increase in Portal Pressure

Abstract

Endothelin-1 (ET-1) is a potent vasoactive peptide which generally exerts its effect on target cells by increasing [Ca++]i. Both vasoconstriction (resulting in an increase in perfusion pressure) and increased [Ca++]i are actions of ET-1 that may result in cholestasis. Single-pass isolated perfused rat liver (IPRL) were used, and [Ca++]i was measured in both populations of hepatocytes and single cells. ET-1 (0.1-100 nM) induced a dose-dependent increase in perfusion pressure and decrease in bile flow. Perfusion pressure increased by 112% (p<0.001) and bile flow decreased by 17% (p<0.008) in response to 2 nM ET-1. At this concentration of ET-1, but not at higher concentrations, the cholestasis was abolished (p>0.18 vs basal) and the rise in perfusion pressure was decreased (by 62%; p<0.002) by the vasodilator papaverine. This ET-1 concentration also had no measurable effect on [Ca++]i in isolated hepatocytes. Taken together these findings indicate that ET-1 inhibits bile flow in IPRL and suggests that this effect is mediated by vasoconstriction and not by changes in hepatocyte cytosolic Ca++.