Effect of Mixed Micellar Lipid on the Absorption- of Cholesterol and Vitamin D3 into Lymph

terol, labeled with tracer doses of cholesterol 14C or cholesterol-'H and of near physiological doses of vita-min D3-'H was studied in rats with cannulated intestinal lymphatics. The effects of administering mixed micellar solutions of fatty acid, monoglyceride, and bile salt on the absorption of these labeled sterols was determined. It was observed that the specific activity of free cho-lesterol and the amounts of vitamin D3 appearing in lymph were significantly increased during the intra-duodenal administration of mixed micellar solutions of either linoleic or palmitic acid, in contrast to control rats receiving a micellar solution of taurocholate. These increases were related linearly to the lymph triglyceride level. In addition it was observed that when the linoleic acid solution was administered there was a more marked increase in the ratio of the specific activities of free and esterified cholesterol in lymph than with either the pal-mitic acid or taurocholate solutions. Additional studies in rats with intact lymphatics showed that the uptake of labeled cholesterol and vitamin D3 from the intestinal lumen into the wall was similar whether the sterols were administered in taurocholate or in mixed micellar solution. These findings suggest that mixed micellar lipid in-creased the rate of appearance of labeled free choles-terol and vitamin Ds in lymph by enhancing their trans-port out of the intestinal mucosa, rather than by an effect on uptake