DIRECT DETERMINATION OF APOLIPOPROTEINS IN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A simple and sensitive high performance liquid chromatographic (HPLC) method is described for the direct quantitation of apolipoproteins (ape) A-I, A-II and B in plasma. The apolipoproteins are well resolved, which allows for quantitation of apo AI, A-II and B and calculation of the ratio of A-I/A-II. Only 10 mu l is required for a single determination of these three apolipoproteins. Compared to other methods requiring separation of HDL by ultracentrifugation and delipidation of apoproteins with organic solvents, this method avoids any loss of apolipoproteins. The HDL in supernatant of plasma precipitated with phosphotungstic acid/magnesium chloride reagent contained essentially all of the plasma ape A-I and ape A-II. However, this supernatant also contained about 37% of plasma apo B, suggesting incomplete precipitation of apoproteins in very low and low density lipoproteins. Thus, this HPLC method can rapidly determine three apolipoproteins in a small volume of plasma without any loss and also can detect incomplete separation of apolipoproteins of very low and low density lipoproteins from HDL fraction.