Absorption of Dihydrocholesterol and Soya Sterols by the Rat's Intestine

Abstract

The rat intestine has a limited capacity to absorb cholesterol. It amounts to approximately 92 mg for a 250 g rat, or 370 mg/kg body weight/day. This has to be considered in the interpretation of results obtained on feeding sterols or mixtures of sterols. An increase in the formation and elimination of sterols which do not develop the Liebermann-Buchard color reaction was not observed until cholesterol was added to the basal diet in excess of the capacity of the sterol absorptive mechanism. Dihydrocholesterol, when fed at a level of 192 mg daily to a 200-250 g male rat, was absorbed to the extent of approximately 22%. It did not influence the elimination of endogenous sterol. Soyo sterol (93% sito-sterol) when fed similarly was also absorbed to the extent of approximately 22%. Evidence of an increase in blood serum sterols was obtained as a result of feeding soya sterols. When 192 mg of dihydrocholesterol and 96 mg of cholesterol were fed together 36% of the cholesterol and 18% of the dihydrocholesterol were absorbed. Since when 96 mg of cholesterol are fed alone, 61% was absorbed, the dihydrocholesterol decreased the absorption of cholesterol by approximately 40%. When a similar mixture of soya sterols and cholesterol was fed, values closely approximating those obtained with dihydrocholesterol were observed. Thus, these sterols decreased the absorption of cholesterol which accounts for the decrease in the blood cholesterol level when they were fed with cholesterol. Cholesterol, dihydrocholesterol, and soya sterols have approximately the same solubility in oleic acid (22%) and in corn oil (3%), at 38[degree]C. Dihydrocholesterol and soya sterols decrease the absorption of cholesterol apparently by competing for the total capacity of the sterol absorptive mechanism on the basis of their relative absorbabilities.