Effects of Cholesterol Feeding on the Bile Acids of Male and Female Germ-Free Rats

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Abstract
The effect of cholesterol feeding on the intestinal bile acids was studied in male and female germ-free rats. The bile acid pattern of the male animals was not altered considerably by cholesterol supplementation. Bile acids belonging to the chenodeoxycholic acid pathway slightly increased whereas cholic acid decreased. β-Muricholic acid remained the predominant bile acid in male rats. On the other hand, cholesterol feeding to female germ-free rats substantially changed the intestinal bile acid composition. The concentration of cholic acid fell to one third and that of β-muricholic acid decreased by about half. On the contrary, the relative amounts of chenodeoxycholic acid, allochenodeoxycholic acid and α-muricholic acid increased several times. The most striking sex-linked effect of cholesterol feeding was the occurrence in female rats of a bile acid tentatively identified as 3α,7β-dihydroxy-6-oxo-5β-cholan-24-oic acid. This bile acid accounted for 16.0% and 26.6% of the total bile acids in the small intestine and in the cecum plus large intestine, respectively. Cholesterol feeding also influenced the sulfation of bile acids in female germ-free rats. In the small intestine the sulfated fraction increased from 1.1% to 2.8% and in cecum plus large intestine from 23.0% to 30.8%. Allochenodeoxycholic acid was the predominant bile acid in the sulfate fraction. The total amount of bile acids in cecum plus large intestine increased from 72.0 to 225.0 mg/kg body weight in male rats and from 64.8 to 231.3 mg/kg body weight in female animals.