Uptake of Cholesterol and Cholesterol Esters by Inverted Sacs of Rat Intestine

Abstract

Conditions for the use of inverted sacs of rat small intestine for the study of the mechanism of cholesterol absorption are described. Incubation of inverted sacs in albumin-stabilized emulsions of free cholesterol or cholesterol esters, under oxygen-carbon dioxide mixture, led to the disappearance of cholesterol from the external medium and accumulation of free or ester cholesterol in the sacs. Both forms of cholesterol were taken up against a concentration gradient without demonstrable chemical change. The uptake of free cholesterol was quite constant from the lower duodenum to the upper ileum and was independent of the pH of the external medium. Additions of oleic acid, sodium taurocholate or pancreatic extract depressed the uptake of free cholesterol. Comparable but more variable effects were found in respect to cholesterol ester uptake. Addition of pancreatic extract to the external medium increased the proportion of ester in the total cholesterol taken up by the sacs. This was due, in part, to synthesis of cholesterol esters in the mucosa.