The relationship between the cholesterol content and subfraction distribution of plasma high-density lipoproteins.

High density lipoprotein subfractions (HDL2 and HDL3) were separated from the plasma of 25 healthy volunteers (13 males, 12 females) rate zonal ultracentrifugation. The rotor elution profile, measured at 280 nm, was used with the specific extinction coefficient for each subfraction (HDL2, 0.60 +/- 0.11 mg protein/A280nm, HDL3, 0.86 +/- 0.10 mg protein/A280nm (n=25) to calculate their plasma concentration. Their protein and lipid composition were also determined by chemical analysis. Plasma lipids, lipoprotein cholesterol, apolipoprotein A-I, apolipoprotein A-II and apolipoprotein B levels were measured in the same subjects and correlated with the HDL subfraction concentrations. HDL cholesterol and apolipoprotein A-I concentrations correlated significantly (p less than 0.01 and 0.02 respectively) with plasma HDL2, but not with HDL3. Indeed, the significantly higher levels of HDL cholesterol and apolipoprotein A-I in the female group could be attributed entirely to an increase in circulating HDL2. This data supports the proposal that the latter subfraction is the major contributor to the anti-atherogenic role of plasma HDL.