A quantitative evaluation of the conversion of 25-hydroxycholesterol to bile acids in man.

The present study was directed toward providing additional information in man on the nature of a potential alternative pathway to cholic acid not involving an initial 7 alpha-hydroxylation of cholesterol. Two bile fistula patients and one normal subject each received 25-hydroxy[G-3H]cholesterol; [14C]cholic and [14C]chenodeoxycholic acids were also simultaneously administered to one bile fistula patient and normal subject. The labeled 25-hydroxycholesterol was found to be poorly converted to primary bile acids by all three patients; the range of conversion was 9.7 to 18.9%. Cholic acid was favored over chenodeoxycholic acid by a margin of about 1.4/1. It is concluded that a pathway to primary bile acid via the 25-hydroxylation of cholesterol is of minor importance under conditions of normal or accelerated synthesis in man.