Influence of bile acids upon biliary cholesterol and phospholipid secretion in the dog.

The relationship between taurocholate or taurochenodeoxycholate secretion and cholesterol and phospholipid secretion in bile was studied in anaesthetized dogs infused with graded doses of these bile acids. Cholesterol output was linearly related to bile acid output during both taurocholate and taurochenodeoxycholate infusions. On the average 1.45 nmol and 4.70 nmol of cholesterol were secreted per mumol of taurocholate or taurochenodeoxycholate respectively (P less than 0.001). A linear relationship was also observed between phospholipid secretion rate and taurocholate or taurochenodeoxycholate secretion rates. However, the amounts of phospholipid secreted per mumol of taurocholate or taurochenodeoxycholate (respectively 0.10 and 0.15 mumol) were not significantly different. Thus, bile was less saturated with cholesterol during taurocholate infusions than during taurochenodeoxycholate infusions. These results are consistent with the hypothesis that micelle formation by bile acids is a major determinant of cholesterol and phospholipid secretion in the dog.