Kinetics of LDL subfractions.
After injecting 125I- or 131I-labeled lipoproteins, plasma was subjected to discontinuous density gradient centrifugation, which separates low-density lipoproteins (LDL) into three subfractions. Analysis of changes in apolipoprotein B-specific activity with time showed that light LDL is normally the product of intermediate-density lipoprotein and the precursor of heavy LDL, which is subsequently converted to heavier LDL. In hyperapobetalipoproteinemia these relationships are maintained but there is overproduction of light and heavy LDL secondary to increased synthesis of very low-density lipoprotein. In familial hypercholesterolemia, light LDL is produced normally but its conversion into heavy LDL is reduced and independent synthesis of the latter is apparent. These observations suggest that the LDL receptor normally plays a role in the conversion of light into heavy LDL. They also provide an explanation for previously documented differences in LDL composition between hyperapobetalipoproteinemia, in which there is a relative increase in cholesterol-depleted heavy and heavier subfractions, and familial hypercholesterolemia, in which there is a relative increase in the cholesterol-enriched light subfraction.
D000818:Animals; D003327:Coronary Disease / Q000209:etiology; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000097:blood / Q000150:complications / Q000378:metabolism; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000097:blood / Q000378:metabolism*; D008970:Molecular Weight; D011817:Rabbits
D008077:Lipoproteins, LDL