Differential transport of cholesterol and oleic acid in lymph lipoproteins: sex differences in puromycin sensitivity.

Adult rats of both sexes were prepared with indwelling drainage catheters in the left thoracic lymphatic duct, and with duodenal infusion catheters. Control and puromycin-treated animals were administered an aqueous test emulsion containing [7alpha-(3)H]cholesterol and [1-(14)C]oleic acid, followed two hours later, by a tracer dose of [1-(14)C]-leucine. Successive 2-hr lymph samples were subjected to ultracentrifugal separations of the major lipoprotein classes. These were specifically extracted for lipids, and for DNA- and lipid-free protein. In both sexes, oleic acid absorption was largely associated with the d < 1.006 g/ml chylomicron fraction throughout the 6-hr experimental period. Small but consistent levels of labeled fatty acid appeared in the 1.006 < d < 1.019 g/ml VLDL fraction. However, with both sexes 25-35% of the absorbed cholesterol appearing in lymph was recovered in the VLDL fraction. Furthermore, there were statistically greater levels of cholesterol in this lymph fraction in females than in males. Cumulative protein levels and leucine incorporation into chylomicron proteins was comparable in both sexes. However, VLDL protein in the female was significantly greater than in the male and this difference was mimicked by the greater incorporation of leucine into VLDL proteins in the female. In males, there were no significant effects of puromycin on cholesterol or oleic acid absorption, despite a marked inhibition in chylomicron protein levels and leucine incorporation into this fraction. There was also no effect of the inhibitor on VLDL protein levels or on leucine incorporation into VLDL peptides. Cholesterol but not oleic acid absorption in females was significantly depressed by administration of puromycin, and this was largely attributed to a decrease in VLDL transport of the sterol. Also, unlike males, leucine incorporation into VLDL peptides was inhibited by 75% by puromycin administration. These results emphasize the importance of non-chylomicron transport of cholesterol during absorption and suggest a hormonal influence on intestinal VLDL synthesis in female rats.-Vahouny, G. V., E. M. Blendermann, L. L. Gallo, and C. R. Treadwell. Differential transport of cholesterol and oleic acid in lymph lipoproteins: sex differences in puromycin sensitivity.