Determinants of the Flow and Composition of Bile in the Unanesthetized Dog during Constant Infusions of Sodium Taurocholate.

Physiological factors affecting the flow and composition of bile may be divided into two general categories. First, the availability of bile salts (by hepatic synthesis and by reabsorption from the bowel) has a significant influence on the rate of bile production. The choleretic effect of natural bile salts and the phenomenon of enterohepatic circulation of these compounds were first demonstrated by Schiff in 1870 (1). These observations have been confirmed by many workers since that time. It has been estimated that 85 to 90 per cent of the bile salt excreted in the bile is reabsorbed and returned to the liver (2, 3). For this reason the entry of bile itself into the duodenum provides a major stimulus for further bile production. Second, factors independent of the availability of bile salts can affect bile production. This category would include, for example, neural stimuli (4, 5), humoral agents such as secretin (6-8) and changes in vascular perfusion (5). During any investigation of biliary secretion in which bile is removed and not replaced, achievement of a steady state is thwarted by progressive depletion of bile salts which would normally undergo enterohepatic circulation. In the present studies this problem has been circumvented by constant intravenous infusion of sodium taurocholate. The results substantiate the important role of active bile salt secretion in the process of bile production and also suggest that the flow and composition of bile are modified by the addition of variable amounts of a solution which is similar in certain respects to pancreatic juice.