Evaluation of the rapid micromethod for ultracentrifugal separation of labeled plasma lipoproteins.

The fractionations of plasma lipoproteins by 2 methods were compared to evaluate the rapid separation (Airfuge) method for lipoprotein distribution studies. When [125I] labeled very low density, low density, and high density lipoproteins (VLDL, LDL, HDL), were separately centrifuged in buffers at d = 1.006, 1.06 or 1.2 g/ml by the conventional ultracentrifuge and the Airfuge, separations of the fractions in the Airfuge were incomplete at both 5 C and 24 C, especially at d = 1.006. [3H] Benzo (a)pyrene, when added to plasma, associates with the plasma proteins and lipoproteins, especially LDL. Compared to the standard techniques, the Airfuge method greatly overestimated its distribution into VLDL. The distribution of [3H] vitamin D3 into the VLDL plus LDL fraction was also overestimated by the Airfuge procedure. It is concluded that caution should be observed in quantitative studies of lipoproteins in the Airfuge. A careful comparison of the distribution into or fractionation of lipoproteins by the 2 methods should always precede any quantitative determinations involving the Airfuge.