Abstract
Small particles of high density lipoproteins (HDL) were isolated from fresh, fasting human plasma and from the ultracentrifugally isolated high density lipoprotein fraction by means of ultrafiltration through membranes of molecular weight cutoff of 70,000. These particles were found to contain cholesterol, phospholipids, and apolipoproteins A-I and A-II; moreover, they floated at a density of 1.21 kg/l. They contained 67.5% of their mass as protein and the rest as lipid. Two populations of small HDL particles were identified: one containing apolipoprotein A-I alone [(A-I)HDL] and the other containing both apolipoproteins A-I and A-II [A-I + A-II)HDL]. The molar ratio of apoA-I to apoA-II in the latter subclass isolated from plasma or HDL was 1:1. The molecular weights of these subpopulations were determined by nondenaturing gradient polyacrylamide gel electrophoresis and found to be 70,000; 1.5% of the plasma apoA-I was recovered in the plasma ultrafiltrate.
Highlights
Small particles of high density lipoproteins (HDL) were isolated from fresh, fasting human plasma and from the ultracentrifugally isolated high density lipoprotein fraction by means of ultrafiltration through membranes of molecular weight cutoff of 70,000.These particles were found to contain cholesterol, phospholipids, and apolipoproteins associated with (A-I) and A-11; they floated at a density of 1.21 kg/l
The results described here indicate the presence of two High density lipoproteins (HDL) subclasses with molecular weights of 70,000; one subclass contains apoA-I alone and the other contains both apoA-I and apoA-I1 at a fixed molar ratio
These groups are heterogeneous in terms of their size; each group comprises two or more subclasses [22], and they differ in their cholesterol content as reported by Ohta et al [7] who found that the (A-1)HDL group contained a significantly lower ratio of cholesteryl ester to total cholesterol than the (A-I + A-1I)HDL group
Summary
Small particles of high density lipoproteins (HDL) were isolated from fresh, fasting human plasma and from the ultracentrifugally isolated high density lipoprotein fraction by means of ultrafiltration through membranes of molecular weight cutoff of 70,000.These particles were found to contain cholesterol, phospholipids, and apolipoproteins A-I and A-11; they floated at a density of 1.21 kg/l. They contained 67.5% of their mass as protein and the rest as lipid. The results described here indicate the presence of two HDL subclasses with molecular weights of 70,000; one subclass contains apoA-I alone and the other contains both apoA-I and apoA-I1 at a fixed molar ratio
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