Cholestatic action of somatostatin in the rat: effect on the different fractions of bile secretion.

Somatostatin was administered intravenously to male Wistar rats, recovered for 3 h from an anesthesia during which the common bile duct and jugular vein were cannulated. Different bile acid-secretory rates were obtained by infusion of saline, or of Na+-taurocholate (150 nmol/min/100 g body wt), or by 8-h bile depletion. At the dose of 2 micrograms/h/100 g body wt, somatostatin causes a prompt decrease of bile flow (about 30%) and of bile acid secretion (32%-47%). The bile acid-independent fraction of canalicular bile is more decreased than the one associated with bile acid secretion. The changes are dose dependent and show a saturation pattern, with half-maximal saturation already at 2.2 ng/min/100 g body wt. Despite this cholestasis, endogenous bilirubin secretion remained unchanged, pointing to different secretory mechanisms for bilirubin and bile acids. In the isolated and perfused liver, somatostatin displays an anticholeretic effect, proportional to the amount of Na+-taurocholate present in the system. Hepatic blood flow and O2 consumption remained constant during perfusion, and were not affected by somatostatin. The hepatic transport of bile acid, and the water and electrolyte secretion are directly affected by somatostatin, and the experimentally-induced cholestasis seems a new and suitable model for studying mechanisms of bile secretion.