title: Apolipoprotein B (B-48) of rat chylomicrons is not a precursor of the apolipoprotein of low density lipoproteins.
abstract: We have found that, in chylomicrons from intestinal lymph fistulas in the rat, the sole molecular species of apolipoprotein B (apo B) is B-48. This protein is analogous to the B-48 apoprotein of human chylomicrons. In contrast, preparations of chylomicrons from blood serum are known to contain species of B apolipoproteins of higher molecular weight, presumably due to the presence of hepatogenous lipoproteins. We studied the removal of 125I-labeled apo B-48 of intestinal lymph chylomicrons from blood plasma of rats. The removal of [14C]cholesteryl esters of biologically labeled chylomicrons was unaffected by radioiodination. The labeled cholesteryl esters and apo B-48 disappeared rapidly from the density (P) less than 1.006 g/ml fraction of plasma. In contrast to the apo B of very low density lipoproteins (1.019 less then p less then 1.063 g/ml) after 1 hr. No 125I was found in the B-100 or B-95 apolipoproteins at any time. We conclude that, unlike the species of apo B found uniquely in hepatogenous very low density lipoproteins, the apo B-48 protein of chylomicrons is not a precursor of the B apoprotein of low density lipoproteins.
mesh_terms: D000818:Animals; D001053:Apolipoproteins / Q000097:blood*; D001055:Apolipoproteins B; D002784:Cholesterol / Q000378:metabolism; D002788:Cholesterol Esters / Q000097:blood; D002914:Chylomicrons / Q000097:blood*; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000096:biosynthesis*; D008196:Lymph / Q000378:metabolism; D051381:Rats
chemical_list: D001053:Apolipoproteins; D001055:Apolipoproteins B; D002788:Cholesterol Esters; D002914:Chylomicrons; D008077:Lipoproteins, LDL; D002784:Cholesterol