METABOLISM OF CONSTITUENT LIPIDS OF DOG CHYLOMICRONS*

Abstract

Chylomicrons in which the different lipids were labeled by separate isotopes were injected intravenously into 5 normal dogs. Radioactivity in triglyceride fatty acids (TGFA), ester cholesterol, and free cholesterol was removed from the chylomicron fraction of plasma lipids at similar rates in 2 dogs. Radioactivity in cholesterol fractions was removed slightly more slowly in 2 of the remaining 3 dogs and much more slowly in the third. Radioactivity in phospholipids was removed at a rate similar to that in TGFA. When chylomicrons were infused into dogs in which the liver was completely or partially excluded from the circulation, radioactivity was removed more slowly in the cholesterol fractions than in the TGFA or phospholipids. In normal dogs, the liver removed almost all the infused chylomicron cholesterol radioactivity, but only a smaller and variable fraction of the TGFA radioactivity. In the functionally hepatectomized dogs, about one-third of the radioactivity removed from chylomicron cholesterol was recovered in adipose tissue.