title: Metabolism of lipoproteins in nonhuman primates. Studies on the origin of low density lipoprotein apoprotein in the plasma of the squirrel monkey.
abstract: The plasma of squirrel monkeys contains extremely low levels of very low density lipoproteins. The delipidated apoproteins from the different lipoprotein density classes of this species show a heterogeneity similar to that of man and the rat. The biosynthesis of the apoproteins of squirrel monkey lipoproteins was studied in fasted normal and Triton WR1339-treated animals. After intravenous injection of [3-H] leucine, maximal labeling of very low density lipoproteins occurred after 1 h, intermediate density lipoproteins (d 1.006--1.019) in 2 h, and low density lipoproteins after 3 h. At all times, however, low density lipoproteins had the greatest percentage of radioactivity. Polyacrylamide gel electrophoresis revealed that the apoprotein B moiety of very low density and intermediate density lipoproteins contained 62% and 81% of the total radioactivity in these lipoproteins whereas the fast-migrating peptides were minimally labeled. In monkeys injected with Triton WR1339, 70--80% of the radioactivity incorporated into d smaller than 1.063 lipoproteins was in very low density lipoproteins with only 10--15% in intermediate and low density lipoproteins. After injection of 3-H-labeled very low density lipoproteins and [14-C] leucine into Triton-treated monkeys, catabolism of 3-H-labeled very low density lipoprotein to intermediate and low density lipoproteins was small and was significantly less than corresponding values for the incorporation of [14-C] leucine. Thus, breakdown of very low density lipoproteins could not account for all the labeled apoprotein B present in the intermediate and low density lipoprotein fractions. The results indicate that most, but not all, of the newly synthesized apoprotein B enters plasma in very low density lipoproteins and that the low concentrations of this lipoprotein in squirrel monkey plasma are a consequence of its rapid turnover.
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000097:blood*; D002784:Cholesterol / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D000882:Haplorhini / Q000097:blood*; D007930:Leucine / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000096:biosynthesis / Q000097:blood; D008077:Lipoproteins, LDL / Q000096:biosynthesis / Q000097:blood*; D008079:Lipoproteins, VLDL / Q000096:biosynthesis / Q000097:blood*; D010743:Phospholipids / Q000032:analysis; D011092:Polyethylene Glycols; D011817:Rabbits / Q000276:immunology; D012453:Saimiri / Q000097:blood*; D014280:Triglycerides / Q000032:analysis
chemical_list: D001059:Apoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D010743:Phospholipids; D014280:Triglycerides; D011092:Polyethylene Glycols; D002784:Cholesterol; D007930:Leucine