COMPARATIVE-STUDIES OF METABOLISM OF SIMULTANEOUSLY ADMINISTERED CHENODEOXYCHOLIC ACID AND URSODEOXYCHOLIC ACID IN HAMSTERS

We present the comparative studies of metabolism of chenodeoxycholic a cid and ursodeoxycholic acid and their taurine conjugates in the liver and fecal culture from hamsters. When [24-C-14]chenodeoxycholic acid and [11,12-H-3]ursodeoxycholic acid were simultaneously instilled into the jejunal loop of bile fistula hamsters, both bile acids administer ed were recovered mainly as their conjugates with taurine and glycine in the fistula bile. The recovery of chenodeoxycholic acid was slightl y but significantly higher than that of ursodeoxycholic acid. Chenodeo xycholic acid was more efficiently conjugated with glycine than ursode oxycholic acid. The glycine/taurine ratio in the biliary chenodeoxycho lic acid was 1.9, and that in ursodeoxycholic acid was 1.6. In additio n, as much as 6.2% of ursodeoxycholic acid was excreted as the unconju gated form; on the other hand only 2.4% of unconjugated chenodeoxychol ic acid was excreted. When [24-C-14]chenodeoxycholyltaurine and [11,12 -(3)]ursodeoxycholyltaurine were simultaneously administered into the ileum loop of bile fistula hamsters, both bile salts were absorbed and secreted efficiently into the bile at the same rate. These results in dicate that slightly lower recovery of ursodeoxycholic acid in the bil e could be due to the less effective conjugation of ursodeoxycholic ac id than chenodeoxycholic acid in the liver. Deconjugation by fecal cul ture from a hamster proceeded more rapidly in chenodeoxycholytaurine t han ursodeoxycholytaurine. 7-Dehyroxylation to form lithocholic acid b y fecal culture was also faster in chenodeoxycholic acid than ursodeox ycholic acid. The formation of 7-oxolithocholic acid from ursodeoxycho lic acid was lesser than from chenodeoxycholic acid. In summary, bacte rial deconjugation followed by 7-dehydroxylation to form lithocholic a cid seems to be achieved more efficiently with chenodeoxycholic acid t han ursodeoxycholic acid.