[Apoprotein B: its plasma level and interaction with cultured fibroblasts]

To study the relationship between the ability of apolipoprotein B (apo B) to interact with LDL receptors and its blood concentration, enzyme immunoassay was used to measure serum apo B levels in 51 healthy donors, 84 patients with coronary heart disease (CHD), and 22 newborns. Employing the same serum samples, the binding of apo B to fibroblasts was determined by the enzyme immunoassay modified for cultured cells. The mean values of apo B concentrations were found to be 0.89 +/- 0.25 mg/ml in the donors, 1.29 +/- 0.51 mg/ml in CHD patients, and 0.57 +/- 0.19 mg/ml in the newborns, while the apo B binding to the cells amounted to 108.9 +/- 16.7, 141.5 +/- 43.6, and 55.0 +/- 24.6 ng/mg, respectively. The mean values of serum apo B binding in the healthy donors and CHD patients were shown to correspond to the concentration relationship of pure LDL interaction with LDL receptors. The findings suggest that higher plasma apo B concentrations in CHD patients cannot be explained by lowered ability of serum apolipoproteins B to interact with LDL receptors of the cells.