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In patients with cholesterol gallstones, there is a diminished bile acid pool and the bile becomes supersaturated with cholesterol. Medical treatment has been aimed at re-expanding the pool to improve cholesterol solubility in bile but as yet the factors controlling the size of the bile acid pool' are unknown. Therefore the role of the liver and intestine in controlling bile acid pool size in the rat was studied and the effect of experimental expansion of the pool on bile acid metabolism and bile lipid composition examined. Bile acid absorption was increased from ileum made hyperplastic by previous jejunectomy and hepatic bile acid synthesis was increased by phenobarbitone treatment. Both jejunal resection and phenobarbitone significantly increased the size of the bile acid pool from 32.2 +/- SEM 0.94 mumoles/100 g body weight to 42.2 +/- 1.71 and 44.4 +/- 2.03 respectively. However, the effects of these experimental manipulations on bile acid secretion rate, enterohepatic cycling frequency, and synthesis rates were quite different. Jejunectomy caused a 56% increase in bile acid secretion and more rapid cycling of the bile acid pool but the enhanced absorption did not depress bile acid synthesis. In contrast, phenobarbitone markedly increased synthesis from 14.5 +/- 1.42 mumoles.100 g BW(-1). 24 hr(-1) to 25.9 +/- 3.19 but there was no significant change in bile acid secretion and the choleresis seen after phenobarbitone was mainly due to an increase in the bile acid-independent fraction of bile flow. In these experimental studies in the rat, expansion of the bile acid pool did not significantly change bile lipid composition or cholesterol solubility in bile.

Although, in suitable patients, oral chenodeoxycholic acid (CDCA) dissolves gallstones, the results of recent animal studies suggest that it might be hepatotoxic. Liver function was therefore studied in patients with gallstones before and during treatment with CDCA and liver biopsies were carried out both in patients with cholelithiasis given bile acid therapy and in those who had been given no medical treatment. In 25 patients treated with 0.5-1.5 g CDCA/day (7-20 mg kg body weight(-1) day(-1)) there was no significant change in serum bilirubin, albumin, globulin, transaminase, isocitric dehydrogenase, alkaline phosphatase, and gamma glutamyl transpeptidase levels before and at monthly intervals during six months' treatment. The kinetics of bromsulphthalein (BSP) clearance and its apparent transport maximum were not significantly changed during CDCA therapy. The mean fasting serum bile acid concentrations of 18.0 +/- SEM 1.2 mumoles/litre before and 20.0 +/- 3.5 mumoles/litre during treatment were both significantly greater than control values. Liver histology was not appreciably different in 11 patients treated with CDCA from that in eight patients with untreated cholelithiasis and in three patients who had received CDCA three to four months before biopsy. These results suggest that in doses of 0.5 to 1.5 g/day CDCA is not hepatotoxic in man.