Benzo[a]pyrene uptake by lymph: a possible transport mode for immunosuppressive chemicals

Benzo[a]pyrene, a lipophilic promutagen, reached maximal concentrations in the thoracic duct lymphatic circulation within 2 h after gastric instillation. Benzo[a]pyrene in lymph obtained by thoracic duct cannulation decreased to approximately control levels within 4 h after treatment. When lymph was not allowed to enter the blood vascular circulation, serum levels of benzo[a]pyrene increased very slowly, suggesting minimal mesenteric blood vascular absorption of the lipophilic hydrocarbon. Benzo[a]pyrene partitions into lymph lipoproteins as a function of the lipoprotein concentration. Data suggest that low-density lipoproteins may take up benzo[a]pyrene more efficiently than do very low-density or high-density lipoproteins, and that lymph components other than lipoproteins do not take up and transport benzo[a]pyrene. We propose that lipophilic xenobiotic compounds interact with cells of the immune system via lymphatic lipoprotein transport of potentially mutagenic, carcinogenic, or immunosuppressive agents.