Apolipoprotein (a) alleles determine lipoprotein (a) particle density and concentration in plasma.

The distribution of Lp(a) lipoprotein (Lp[a]) and genetic apolipoprotein(a) (apo[a]) isoforms in plasma samples from 29 healthy normolipidemic subjects of known apo(a) phenotype was evaluated by density gradient ultracentrifugation. The density of Lp(a) was directly related to the size of the apo(a) isoform, ranging from 1.043 g/ml for the LpF phenotype to 1.114 g/ml for the LpS4 phenotype. Heterozygotes had two distinct Lp(a) particles, each containing one of the respective isoforms in plasma. In each heterozygote, the concentration of the lighter Lp(a) species was higher than that of the denser Lp(a) population. These data suggest that apo(a) alleles determine the density and the metabolism and thereby also the concentrations of Lp(a) particles in plasma.