Conversion of Cholesterol to Trihydroxycoprostanic Acid and Cholic Acid in Man*

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Abstract
After intravenous administration of cholesterol-4-C14 to a patient with a bile fistula, a cholesterol metabolite, trihydroxycoprostanic acid-4-C14 was isolated from the bile, identified, and crystaUized to constant specific activity. This product was given intravenously to a second bile fistula patient; and cholic acid-4-C14, the major radioactive compound excreted, was isolated from the bile, identified, and crystallized to constant specific activity. This study has led to these conclusions: Trihydroxycoprostanic acid is a naturaUy occurring intermediate in the conversion of cholesterol to cholic acid in man. Cholic acid is the major product of trihydroxycoprostanic acid oxidation in man. Trihydroxycoprostanic acid may be regarded as another human primary bile acid. Small amounts of trihydroxycoprostanic acid may be excreted without further oxidation by the Uver in bile fistula patients.