Formation of bile acids in man. Metabolism of 7alpha-hydroxy-4-cholesten-3-one in normal subjects with an intact enterohepatic circulation.

The formation of bile acids in man is thought to involve a series of reactions in which the initial steps are the same for both cholic acid and chenodeoxycholic acid. The point of bifurcation of the pathway is postulated to occur after the formation of 7alpha-hydroxy-4-cholesten-3-one. To test the hypothesis that the entire synthesis of both bile acids proceeds through this intermediate we studied the metabolism of labeled 7alpha-hydroxy-4-cholesten-3-one in eight normal subjects with an intact enterohepatic circulation. If all the production of cholic acid and chenodeoxycholic acid takes place via 7alpha-hydroxy-4-cholesten-3-one, the areas under the specific decay curves of cholic acid and chenodeoxycholic acid should be identical following a single injection of this labeled intermediate. However, in 6 of the 8 subjects studied the area under the cholic acid specific activity decay curve was significantly less than the area under the chenodeoxycholic acid specific activity decay curve. These results that the production of cholic acid in man may not always involve the intermediate 7alpha-hydroxy-4-cholesten-3-one.