Studies on the ability of rat lung and liver microsomes to facilitate transfer and metabolism of benzo[a]pyrene from diesel particles.
Little is known about the bioavailability of inhaled organic compounds that are associated with particles. It is known that certain particle-associated organic compounds, such as polycyclic aromatic hydrocarbons (PAH) adsorbed on diesel soot particles, are retained in the lung longer than PAH inhaled in pure form. If such particle-associated compounds are available for tissue interaction, their prolonged retention may result in an increased potential for a toxic effect. To determine the factors affecting the bioavailability of particle-associated PAH, we have studied the ability of microsomes to facilitate transfer of benzo[a]pyrene (B[a]P) adsorbed on the surface of diesel exhaust soot particles to the microsomes and the ability of the microsomes to metabolize the transferred B[a]P. Our results indicate that rat lung and liver microsomes were able to facilitate the transfer of small amounts of B[a]P from diesel particles (less than 3%), but only a fraction of the amount transferred (1-2%) was metabolized. Under the same incubation conditions without soot, free B[a]P was extensively metabolized by microsomes, principally to B[a]P-9,10-diol. Lung microsomes were about twice as effective as liver microsomes for the transfer of the B[a]P. The ability to transfer B[a]P to the microsomes was independent of metabolism or the presence of protein, but was related to the lipid content of the microsomal fraction. There was no metabolism of the B[a]P coated on diesel particles as analyzed by high-performance liquid chromatography. These findings suggest that microsomes are able to enhance the slow transfer of only a small amount of B[a]P from diesel particles in a form that can be metabolized. However, over a long period of time, this slow release might be significant.
Leung
H W
HW
Inhalation Toxicology Research Institute, Albuquerque, NM 87185.
Henderson
R F
RF
Bond
J A
JA
Mauderly
J L
JL
McClellan
R O
RO
D000327:Adsorption; D000818:Animals; D001564:Benzo(a)pyrene / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D050356:Lipid Metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D001335:Vehicle Emissions
D001335:Vehicle Emissions; D001564:Benzo(a)pyrene