Bile Formation in the Intact Pig

SUMMARY Bile formation was studied in nonanesthetized Swiss large white pigs, previously cholecystectomized and equipped with a Thomas duodenal cannula, during intravenous infusions of sodium taurocholate. Relative steady states of bile flow were achieved by cholinergic blockade. With bile salt excretions ranging from 18 to 118 μEq/minute, linear relationships were obtained for bile flow and elimination of inorganic electrolytes. Thus, 0.01 ml of water, 1.87 μEq of Na+, 0.06 μEq of K+, 0.24 μEq of HCO3−, and 0.69 μEq of Cl− were excreted per microequivalent of bile salt. It was possible to define a bile salt-independent fraction of bile, averaging 0.15 ml/minute. In 2 short-term studies (with pigs given general anesthesia), canalicular bile formation was assessed, using 14C-erythritol. At low flow rates, clearance values were identical with the collected bile volume. At high flow rates, however, bile flow exceeded erythritol clearance by approximately 10%. From these results, it may be concluded that in the pig bile formation depends mainly on the excretion of bile salts. In addition, a bile salt-independent fraction, largely of hepatocytic origin, may be defined.