CHYLOMICRON TRIACYLGLYCEROL FATTY-ACIDS IN SUCKLING NORTHERN ELEPHANTSEALS (MIROUNGA-ANGUSTIROSTRIS) RESEMBLE THE COMPOSITION AND THE DISTRIBUTION OF FATTY-ACIDS IN MILK-FAT

Following birth, the northern elephant seal (Mirounga angustirostris) pups rapidly gain weight by ingesting milk with a high fat content, as much as 50%. To better understand the metabolism of the pups during t he suckling period, the positional distributions of triacylglycerol fa tty acids in both the milk and chylomicra were determined. Extracts of enzymatically digested lipids were separated by thin layer chromatogr aphy and the constituent fatty acids were separated and quantified by gas liquid chromatography. Over 84% of the fatty acids were either mon oenoic or saturated, with the ratio of monoenoic to saturated fatty ac ids ranging between 2.9-4.0. Positional distributional analyses reveal ed that the very long chain monoenoics (20:1 and 22:1) were located pr imarily at the sn-1,3 positions of milk triacylglycerols. In the inter val between the onset of lactation to the time of weaning, the content of these very long chain monoenoic fatty acids at the sn-1,3 position s increased from 13-37%. At the sn-2 position, the percentage of 18: 1 was 3-5-fold higher than 16:1. Analyses indicated that the triacylgly cerols in both milk and suckling pup chylomicra were similar. This par ticularly was true for the distributions at the sn-2 position, indicat ing that milk fats are being absorbed primarily via the 2-monoacylglyc erol pathway.