The quantitative determination of apolipoprotein A-I (apo-lp-Gln I) in human serum by radial immunodiffusion assay (RID).

A radial immunodiffusion (RID) assay was developed to determine the concentration of the major apolipoprotein (apolipoprotein A-I, apo-lp-Gln I) of human high density lipoproteins (HDL): (1) In a random population sample of apparently healthy persons (104 women, 95 men) aged 40-49 years, serum levels of apo A-I were determined. For both women and men a value of 137 +/- 23 mg/dl was found. (2) Values of 139 +/- 21 mg/dl were found in a group of 31 women taking oral contraceptives, i.e. an insignificant increase in apo A-I level. (3) In two volunteers, apo A-I levels showed no significant variation in a 24-h period.