Metabolic heterogeneity of post-lipolysis rat mesenteric lymph small chylomicrons produced in vitro.
The study was undertaken to investigate the metabolic rat of post-lipolysis mesenteric lymph small chylomicrons produced in vitro. Small chylomicrons doubly labeled with [3H]cholesterol (more than 70% in cholesteryl esters) and [14C]palmitate-labeled triglycerides were collected from rat mesenteric lymph during periods of fasting. Lipolysis was performed in vitro with lipoprotein lipase purified from bovine milk. More than 98% of the chylomicron-triglycerides could be hydrolyzed to fatty acids. Post-lipolysis chylomicrons were separated by zonal ultracentrifugation, characterized, and tested for biological behavior in intact rats. Following lipolysis the lipoproteins lost nearly all their triglycerides, apoA-I, and apoC, and were relatively enriched with cholesteryl esters, unesterified cholesterol, phospholipids, and apoB. Three preparations were tested for biological behavior: pooled (total) post-lipolysis chylomicrons (diameter approximately 250 A); particles at the ascending part of the zonal effluent (diameter approximately 300 A), and at the descending part (diameter approximately 200 A). After intravenous injection to intact rats, [3H]cholesteryl ester decay was very rapid with pooled lipoproteins and the 300-A preparation (t1/2 = 5-10 min). The 200-A preparation in contrast stayed in circulation much longer (t1/2 = 60-90 min). The study thus  demonstrated metabolic heterogeneity of post-lipolysis small chylomicrons and indicated that some may form an LDL-like subpopulation with a plasma lifetime slower than "remnants" but faster than LDL.
D000818:Animals; D002501:Centrifugation, Zonal; D055598:Chemical Phenomena; D002621:Chemistry; D002914:Chylomicrons / Q000378:metabolism*; D006868:Hydrolysis; D066298:In Vitro Techniques; D008066:Lipolysis; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D008196:Lymph / Q000378:metabolism*; D008297:Male; D051381:Rats
D002914:Chylomicrons; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL