Differential turbidimetric assay for subpopulations of lipoproteins containing apolipoprotein A-I.

A differential immunoturbidimetric procedure for the quantitation of apolipoprotein A-I associated with lipoproteins LpA (containing both apolipoprotein A-I and apolipoprotein A-II) and with lipoproteins LpA-I (containing apolipoprotein A-I but no apolipoprotein A-II) is presented. Lipoproteins containing apolipoprotein A-II are precipitated with an anti-apolipoprotein A-II antibody. The resulting immunoprecipitate is sedimented and LpA-IA-I is measured in the supernate. Whereas LpA-IA-I concentrations differed significantly between normolipidaemic men and women (0.75 and 1.00 g/l, respectively), there was virtually no sex related difference in LpAA-I (0.83 and 0.88 g/l, respectively). LpA-IA-I was predominantly correlated with HDL2-cholesterol (rs = 0.630), whereas LpAA-I was statistically associated with HDL3 (rs = 0.417).