Influence of dietary cholesterol on excretion of cholesterol-4-C¹⁴ by the rat

¹ Department of Internal Medicine, The University of Texas Southwestern Medical School, Dallas, Texas

The influence of dietry cholesterol on the excretion of cholesterol-4-C¹⁴ has been studied in rats pair fed isocaloric quantities of purified diets supplemented with varying amounts of cholesterol and either oleic or linoleic acid. Of the C¹⁴ excreted over an 8-day period, slightly more than half was present in the neutral sterol fraction of feces from rats fed sterol-free diets. The addition of dietary cholesterol, however, under circumstances where significant cholesterol absorption was promoted by the addition of fatty acids to the diets, resulted in a reversal of this ratio so that the bile acid fraction accounted for the major portion of excreted cholesterol-C¹⁴. Cholesterol balance data revealed that the degradation rate of cholesterol in these animals rose to about 17–20 mg/day. These data are interpreted as demonstrating that the amount of absorbed dietary cholesterol plays a crucial role in determining both the relative and absolute importance of the two major routes of cholesterol excretion.