Benzo(a)pyrene uptake by human plasma lipoproteins in vitro.

The possible role of human plasma lipoproteins as car riers in the transport of the carcinogen, benzo(a)pyrene, was assessed in in vitro studies. [14C]Benzo(a)pyrene was incubated in whole human blood, plasma, or isolated lipo protein fractions. Benzo(a)pyrene d istribution between plasma and red blood cells was estimated following sedi mentation of red blood cells. Benzo(a)pyrene distribution in the major lipoprotein fractions was determined following ultracentrifugal fractionation of plasma. Greater than 70% of benzo(a)pyrene in whole blood partitioned into plasma. Of the benzo(a)pyrene in plasma, less than 5% partitioned into the bulk of the plasma proteins (d > 1.21 g/ml), while more than 95% partitioned into the plasma lipoproteins (d < 1 .21 g/ml). The distribution of benzo(a)pyrene in normo lipoproteinemic plasma was 29% in very-low-density (d < 1.006 g/ml), 57% in low-density (d 1.006-1.063 g/ml), and 10% in high-density (d 1.063-1.21 g/ml) lipoproteins. The percentage of benzo(a)pyrene d istribution among lipo pro tein fractions was independent of the level of benzo (a)pyrene taken up by plasma. It was also independent of whether the incubation studies were conducted with total plasma subsequently fractionated into lipoprotein fractions or with isolated lipoprotein fractions themselves, which yielded a calculated percentage of distribution. Benzo(a)pyrene uptake by lipoproteins was correlated with lipoprotein-total lipid volume for isolated very-low density, low-density, and high-density lipoproteins. [“C] Benzo(a)pyrene incorporated into chylomicrons or isolated lipoprotein fractions transferred from chylomicron to lipo proteins and among lipoproteins, respectively. These findings are discussed with respect to (a) the use of the uptake data to estimate percentage of benzo (a)pyrene distribution for other plasmas, (b) factors which may govern benzo(a)pyrene distribution in plasma of intact animals, (C) the possible relationship in the intact animal between lipoprotein and benzo(a)pyrene turnover, and (d) the possible role of lipoproteins in cellular uptake of benzo(a)pyrene.