Distribution of toxaphene, DDT, and PCB among lipoprotein fractions in rat and human plasma.

The distribution of 14C-toxaphene, 14C-DDT, and 14C-PCB among lipoprotein fractions was studied in vitro and in vivo using rat and human plasma. The association of these substances with rat plasma fractions was similar in both in vitro and in vivo experiments. Thirty-seven to fifty-two per cent of the total radioactivity was associated with the cholesterol-rich high density lipoproteins (HDL2, d = 1.075-1.21 g/ml) and 18-52% was recovered in the albumin-rich bottom fraction (BF, d greater than 1.21 g/ml). A time-dependent redistribution of the radioactivity from the lipoprotein fractions to the BF was also observed in the in vivo studies. In human plasma, the distribution of the three compounds was different and uncorrelated to the cholesterol level of the individual lipoprotein fractions. Toxaphene was almost equally distributed between BF (d greater than 1.21 ml), HDL (d = 1.063-1.21 g/ml) and low density lipoproteins (LDL, d = 1.006-1.063 g/ml) (26%, 27% and 29%, respectively), while only 18% appeared in the very low density lipoprotein (VLDL, d less than 1.006) fraction. In contrast, a large proportion of DDT and PCB radioactivity was recovered in the BF (52% and 62%, respectively) while only 38-48% was present in lipoprotein fractions. The complex nature of the interaction between xenobiotics and plasma lipoproteins is discussed.