Evaluation of a new precipitation procedure for estimating high density lipoprotein cholesterol: precipitation of apolipoprotein B associated cholesterol with concanavalin A.

The implication of HDL as a negative risk factor in cardiovascular disease has focused on the need for an accurate but rapid routine method for determining HDL-cholesterol in human serum. A practical approach is the specific precipitation of apo-B-containing lipoproteins (atherogenic lipoproteins) by Concanavalin A (Con. A), a lectin with high affinity for glycoprotein apo-B. Specificity was assessed by radial immunodiffusion of apoprotein B in whole serum and in Con. A supernates. Double-immunodiffusion of isolated LP-fractions against anti-apo-B and Con. A demonstrated immunochemical identity of Con. A precipitable LP with apo-B-containing LP. Con. A precipitated cholesterol in the d : 1.063-1.21 g/ml fraction when apo-B was present. Complete precipitation of low density cholesterol was demonstrated, using a reconstituted serum sample radiolabelled in the d less than 1.063 g/ml fraction. Treatment of a reconstituted serum sample containing radiolabelled 125I-apo-A-I with Con. A demonstrated precipitation of trace amounts only of apo A-I. Con. A precipitated LP-B cholesterol quantitatively even when serum triglycerides (TG) exceeded 37.7 mmol/l. Clinical application of this method revealed that 73% of the patient population demonstrated apo-B in the d greater than 1.063 g/ml fraction.