Incorporation of Dietary Lecithin and Lysolecithin into Lymph Chylomicrons in the Rat

Abstract

Incorporation of dietary phospholipids into lymph chylomicrons was studied in rats fed corn oil containing either radioactive lecithin or lysolecithin. The specific activity of lecithin-32P in chylomicrons relative to that in the oil increased directly with the amount of lecithin fed, whereas the lecithin content of chylomicrons was constant. About 40% of the phospholipid in chylomicrons was derived from the meal when the lecithin content of the meal was 6 to 11%. When 1-palmitoyl-9,10-3H-lecithin-32P was fed, one-fifth of the 3H recovered in chylomicrons was present in lecithin and the ratio of 3H:32P in lecithin in chylomicrons was the same as that in the oil. When 1-palmitoyl-9,10-3H, 2-linoleoyl-1-14C-lecithin-32P was fed, 5% of the 14C recovered in chylomicrons was found in lecithin, and the ratios of 14C:3H and of 14C:32P in chylomicron lecithin were only 20% of that in the lecithin fed. The ratio of choline-3H to 32P in lecithin of chylomicrons collected from rats fed choline-(methyl)-3H lecithin-32P was the same as that in the oil meal. Up to 40% of 1-acyl lysolecithin-32P fed with corn oil was recovered in chylomicron lecithin in 6 hours. The findings indicate that dietary lecithin is hydrolyzed and absorbed as lysolecithin and subsequently reacylated before being incorporated into lymph chylomicrons.