Composition of lymph chylomicrons from proximal or distal rat small intestine.

The composition of lymph chylomicrons secreted by rat proximal and distal small intestine were compared during constant perfusion of a lecithin-stabilized tri (1-14C) oleoyl glycerol emulsion, in pairs of unanesthesized rats with mesenteric lymph fistulas. By the 6th hr of infusion when 14C-triglyceride output was constant, the distal intestine secreted 33% less chylomicron phospholipid. Distal chylomicrons were larger and had higher triglyceride:phospholipid and higher apoprotein:phospholipid ratios than chylomicrons secreted by proximal intestine. The major apoprotein classes--apoB, apoA-I, apoE(= ARP), and C peptides--were present in both groups of chylomicrons, but in different proportions. Distal chylomicrons contained less apoA-I and more C peptides, with an increase in apoC-III3, and a decrease in apoC-III0, compared with proximal chylomicrons. The present study suggests that the distal intestine is defective in the utilization of phospholipid from the intestinal lumen for chylomicron phospholipid synthesis. Whether the observed changes in the size and phospholipid or apoprotein content of distal chylomicrons affect their system metabolism is presently not known.