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®.