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 [ 125 I] 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. [ 3 H] 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 [ 3 H] vitamin D 3 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 ® .