Differential effect of ultracentrifugation on apolipoprotein A-I-containing lipoprotein subpopulations.
Two populations of apolipoprotein (apo) A-I-containing lipoprotein particles are found in high density lipoproteins (HDL): those that also contain apo A-II[Lp(A-I w A-II)] and those that do not [Lp(A-I w/o A-II)]. Lp(A-I w/o A-II) comprised two distinct particle sizes with mean hydrates Stokes diameter of 10.5 nm for Lp(A-I w/o A-II)1 and 8.5 nm for Lp(A-I w/o A-II)2. To study the effect of ultracentrifugation on these particles, Lp(A-I w/o A-II) and Lp(A-I w A-II) were isolated from the plasma and the ultracentrifugal HDL (d 1.063-1.21 g/ml fractions) of five normolipidemic and three hyperlipidemic subjects. The size subpopulations of these particles were studied by gradient polyacrylamide gel electrophoresis. Several consistent differences were detected between plasma Lp(A-I w/o A-II) and HDL Lp(A-I w/o A-II). First, in all subjects, the relative proportion of Lp(A-I w/o A-II)1 to Lp(A-I w/o A-II)2 isolated from HDL was reduced. Second, particles larger than Lp(A-I w/o A-II)1 and smaller than Lp(A-I w/o A-II)2 were considerably reduced in HDL. Third, a distinct population of particles with approximate Stokes diameter of 7.1 nm usually absent in plasma was detected in HDL Lp(A-I w/o A-II). Little difference in subpopulation distribution was detected between Lp(A-I w A-II) isolated from the plasma and HDL of the same subject. When plasma Lp(A-I w/o A-II) and Lp(A-I w A-II) were centrifuged, 14% and 4% of A-I were, respectively, recovered in the D greater than 1.21 g/ml fraction. Only 2% A-II was found in this density fraction. These studies show that the Lp(A-I w/o A-II) particles are less stable than Lp(A-I w A-II) particles upon ultracentrifugation. Among the various Lp(A-I w/o A-II) subpopulations, particles larger than Lp(A-I w/o A-II)1 and smaller than Lp(A-I w/o A-II)2 are most labile.
D000328:Adult; D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A / Q000097:blood*; D001057:Apolipoproteins E / Q000097:blood; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005260:Female; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood; D008055:Lipids / Q000097:blood; D008075:Lipoproteins, HDL / Q000097:blood*; D008297:Male; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000097:blood; D013861:Thiocyanates / Q000494:pharmacology; D014461:Ultracentrifugation
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D001054:Apolipoproteins A; D001057:Apolipoproteins E; D008055:Lipids; D008075:Lipoproteins, HDL; D013861:Thiocyanates; D007862:Phosphatidylcholine-Sterol O-Acyltransferase