Circadian distribution of bile acid in the enterohepatic circulatory system in hamsters.

The distribution of bile acid in the enterohepatic circulatory system at different times of the day was determined in 48 hamsters exposed to a rigid light schedule (6 AM to 6 PM) and fed, ad libitum, for 4 weeks. In each portion of the enterohepatic circulatory system, the relative amount of bile acid was determined 24 hours after an intraperitoneal administration of [3H]taurocholic acid by comparing the radioactivity recovered from that portion with the total radioactivity remaining in the entire system. A circadian fluctuation of the relative bile acid content (percent of total) was observed in serum, liver, gallbladder, and intestinal contents. The patterns of such rhythmic change varied in various segments of the intestinal tract but correlated well with the time sequence of the movement of bowel content. Rhythms in the serum and liver were intimately related to the intestinal absorption of bile acid. Due to its small capacity, the gallbladder played only a minor role in the regulation of such a rhythm.