Factors Facilitating Cholesterol Absorption From the Intestine Via Lymphatic Pathways

¹ From the Department of Biochemistry, George Washington University School of Medicine, Washington, D. C.

The lipid fractions of thoracic duct lymph in unanesthetized rats were determined following intragastric administration of saline-albumin emulsions containing various combinations of cholesterol, taurocholate and oleic acid. Sodium taurocholate or oleic acid alone produced significant increases in the total lipid, neutral fat and phospholipid fractions, but had no effect on the level of free and ester cholesterol. Administration of cholesterol alone was without effect on any of the fractions. The combination of taurocholate and oleic acid gave the same levels of lipid fractions as when they were administered singly except that there was an elevation of ester cholesterol indicating increased absorption of endogenous cholesterol. Cholesterol plus taurocholate or oleic acid produced the same increases in the fractions as the salt or acid alone except that with both combinations there were highly significant increases in the total and ester cholesterol fractions. Administration of the three factors together gave further increases in all fractions except neutral fat and free cholesterol. The amount of free cholesterol was constant throughout all groups, even in those in which there was absorption of exogenous cholesterol. The percentage of ester cholesterol in the total cholesterol of lymph ranged from 66 to 81 with the higher percentages in the groups where cholesterol absorption occurred. The esterification of the ‘extra’ cholesterol in lymph due to cholesterol absorption ranged from 86 to 92%. It is suggested that essentially all of the cholesterol transferred from the intestinal lumen to the lacteals is esterified.