Oxidoreduction of different hydroxyl groups in bile acids during their enterohepatic circulation in man

The extent of oxidoreduction of the 3 alpha-, 7 alpha- and 12 alpha-hydroxyl groups in bile acids during the enterohepatic circulation in man was studied with the use of [3 beta-3H]-labeled deoxycholic acid and cholic acid, [7 beta-3H]-labeled cholic acid, and [12 beta-3H]-labeled deoxycholic acid and cholic acid. Each [3H]-labeled bile acid was given per os to healthy volunteers, together with the corresponding [24-14C]-labeled bile acid. The rate of oxidoreduction was calculated from the decrease in the ratio between 3H and 14C in the respective bile acid isolated from duodenal contents collected at different time intervals after administration of the labeled bile acids. The mean fractional conversion rate was found to be 0.29 day-1 for the 3 alpha-hydroxyl group in deoxycholic acid (n = 2), 0.18 day-1 for the 12 alpha-hydroxyl group in deoxycholic acid (n = 6), 0.09 day-1 for the 3 alpha-hydroxyl group in cholic acid (n = 3), 0.05 day-1 for the 7 alpha-hydroxyl group in cholic acid (n = 2), and 0.03 day-1 for the 12 alpha-hydroxyl group in cholic acid (n = 2). The extent of oxidoreduction of the 12 alpha-hydroxyl group in [12 beta-3H]-labeled deoxycholic acid given to two patients operated with subtotal colectomy and ileostomy was markedly reduced (less than 20% of normal).(ABSTRACT TRUNCATED AT 250 WORDS)