Transfer of polycyclic aromatic hydrocarbons between model membranes: relation to carcinogenicity.

Polynuclear aromatic hydrocarbons (PAH), some of which are potent carcinogens, are common environmental pollutants. The transport processes for these hydrophobic compounds into cells and between intracellular membranes are diverse and are not well understood. A common mechanism of transport is by spontaneous desorption and transfer through the aqueous phase. From the partitioning parameters, we have inferred that the rate limiting step involves solvation of the transfer species in the interfacial water at the phospholipid surface. Transfer of 10 PAH (pyrene, 3,4-benzophenanthrene, triphenylene, chrysene, 1,2-benzanthracene, 1,1'-binaphthyl, 9-phenylanthracene, 2,2'-binaphthyl, m-tetraphenyl and 1,3,5-triphenylbenzene) out of phosphatidylcholine vesicles has been examined. Our results show that the molecular volume of the PAH is a rate-determining factor. Moreover, high performance liquid chromatography (HPLC) data confirms the hypothesis that the rate of transfer is correlated with the size of the molecule and with the partitioning of the molecule between a polar and hydrocarbon phase. The kinetics and characteristics of the spontaneous transfer of carcinogens are likely to have a major impact on the competitive processes of PAH metabolism within cells.