Conversion of Δ5,7-Cholestadien-3β-ol to 3α, 7α, 12α-Trihydroxy-5β-cholanoic Acid in the Bile Fistula Rat

The present study has shown that labeled cholic acid is a major metabolite formed when 7-dehydrocholesterol-4-14C is fed to bile fistula rats. Since biliary and hepatic cholesterol were essentially devoid of radioactivity, it has been postulated that the biogenesis of cholic acid under these conditions may proceed either through a pathway that excludes cholesterol as a metabolic intermediate or through a small pool of cholesterol which is being actively converted to bile acids. In intact rats, however, the efficient conversion of 7-dehydrocholesterol to cholesterol was shown. The results are discussed in the light of recent observations that naturally occurring sterols containing 27 carbon atoms could be oxidized to more polar products by microsomal enzymes similar to those which catalyze hydroxylation reactions in the early stages of bile acid biogenesis.