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Although several studies have demonstrated an inverse relationship between size of the bile salt pool and frequency of enterohepatic cycling, most such data have been obtained in conditions where control of cycling frequency was not possible. In this study, we diverted bile from the bile duct of Rhesus monkeys into a reservoir and returned it to the duodenum at varying rates, a model that mimicked differences in frequency of gallbladder emptying. As cycling frequency increased from 1 to 8 cycles/day, size of the bile salt pool decreased from 1756 microM to 369 microM. Changes in fractional turnover rate parallelled changes in cycling frequency. The relative composition of the biliary lipids remained the same throughout the range of cycling frequencies. These data show that direct manipulation of cycling frequency had the predicted effects on other parameters of the enterohepatic circulation but did not give rise to lithogenic bile.

The effects of cholecystectomy upon bile salt kinetics were studied in normal guinea pigs. After cholecystectomy, bile salt pool size decreased, fractional daily turnover rate increased, and the rate of bile salt synthesis was unchanged. These data indicate that an increased frequency of bile salt enterohepatic cycling is sufficient to produce alterations in bile salt kinetics. Abnormalities of bile salt synthesis need not be present in order for a reduction in pool size to occur.