Abstract
Milligram amounts of [3 beta-3H]lithocholic (3 alpha-hydroxy-5 beta-cholanoic) acid were administered by intravenous infusion to rats prepared with a biliary fistula. Analysis of sequential bile samples by thin-layer chromatography (TLC) demonstrated that lithocholic acid glucuronide was present in bile throughout the course of the experiments and that its secretion rate paralleled that of total isotope secretion. Initial confirmation of the identity of this metabolite was obtained by the recovery of labeled lithocholic acid after beta-glucuronidase hydrolysis of bile samples. For detailed analysis of biliary metabolites of [3H]lithocholic acid, pooled bile samples from infused rats were subjected to reversed-phase chromatography and four major labeled peaks were isolated. After complete deconjugation, the two major compounds in the combined first two peaks were identified as murideoxycholic (3 alpha, 6 beta-dihydroxy-5 beta-cholanoic) and beta-muricholic (3 alpha, 6 beta, 7 beta-trihydroxy-5 beta-cholanoic) acids and the third peak was identified as taurolithocholic acid. The major component of the fourth peak, after isolation, derivatization (to the methyl ester acetate), and purification by high pressure liquid chromatography (HPLC), was positively identified by proton nuclear magnetic resonance as lithocholic acid 3 alpha-O-(beta-D-glucuronide). These studies have shown, for the first time, that lithocholic acid glucuronide is a product of in vivo hepatic metabolism of lithocholic acid in the rat.
Highlights
Milligram amounts of [3P-3H]lithocholic (3a-hydroxy5P-cholanoic) acid were administered by intravenous infusion to rats prepared with a biliary fistula
The major objective of the studies was to determine whether lithocholic acid glucuronide is a product of the hepatic metabolism of lithocholic acid in the rat and, if so, whether its presence could be correlated with cholestasis
Cholestasis could be consistently produced only in rats whose endogenous bile acid pool had been depleted by overnight biliary drainage
Summary
Milligram amounts of [3P-3H]lithocholic (3a-hydroxy5P-cholanoic) acid were administered by intravenous infusion to rats prepared with a biliary fistula. For detailed analysis of biliary metabolites of [3H]lithocholic acid, pooled bile samples from infused rats were subjected to reversed-phase chromatography and four major labeled peaks were isolated. The major component of the fourth peak, after isolation, derivatization (to the methyl ester acetate), and purification by high pressure liquid chromatography (HPLC), was positively identified by proton nuclear magnetic resonance as lithocholic acid 3a-O-(P-D-glucuronide). These studies have shown, for the first time, that lithocholic acid glucuronide is a product of in vivo hepatic metabolism of lithocholic acid in the rat. Metabolism of lithocholic acid in the rat: formation of lithocholic acid 3-0glucuronide in vivo. 6P-hydroxylation in the rat detoxifies lithocholic acid but is a salvage pathway that returns the hydroxylated products to the bile acid pool
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