243 Blochzmlca et Bmphyswa Acta, 629 (1980) 243--258 © Elsevier/North-Holland Bmrnedmal Press BBA 29225 TRANSPORT OF A CARCINOGEN, BENZO[a]PYRENE, FROM PARTICULATES TO LIPID BILAYERS A MODEL FOR THE FATE OF PARTICLE-ADSORBED POLYNUCLEAR AROMATIC HYDROCARBONS WHICH ARE RETAINED IN THE LUNGS JOSEPH R. LAKOWICZ, DAVID R BEVAN and STEVEN C. RIEMER Department of Blochemzstry and Gray Freshwater Bzologwal Institute, University of Minnesota, P O. Box 100, Navarre, MN 55392 (U.S A ) (Received October 23rd, 1979) Key words Benzo[a]pyrene, Lung retentmn, Carcinogen transport, Lzp~d bilayer Summary Fluorescence spectroscopic methods were used to investigate the effects of adsorption of benzo[a]pyrene to particulate matter on its rate of uptake into model membranes composed of dipalmitoyl L~-phosphatidylcholine. From these experiments we conclude the following: 1. Adsorption of benzo[a]pyrene to four types of asbestos (anthophyllite, crocidolite, chrysotile, and amosite) and a variety of non-fibrous particles (hematite, silica, titanium dioxide, porous glass and talc) results in increased rates of membrane uptake when compared with aqueous suspensions of benzo- [a]pyrene microcrystals. Benzo [a]pyrene was not released from carbon black. 2. Asbestos-adsorbed benzo[a]pyrene was transferred to the membranes most rapidly. 3. Adsorption of benzo[a]pyrene to the surface of the particles is necessary for its enhanced transport into membranes. That is, simple mixtures of benzo- [a]pyrene microcrystals and particulates do not show enhanced transport. 4. Partmle-enhanced transport of benzo[a]pyrene is not correlated with the effects of the particles on vesicle integrity, binding of vesicles to the particles, or the concentrations of either particles or vesicles. The rate limiting step for transport of benzo[a]pyrene into vesicles appears to be its rate of desorption from the surface of the particle. Following desorption, membrane uptake of benzo [a ] pyrene is rapid. Abbrevmtlon: DPPC, dlpaln~toyl phosphatldylchohne.