Effects of crocidolite and chrysotile asbestos on cellular uptake and metabolism of benzo(a)pyrene in hamster tracheal epithelial cells

Abstract

The incidence of bronchogenic carcinoma is increased substantially in asbestos workers who smoke. We used several approaches to determine possible mechanisms of synergism at the cellular level between asbestos and the polycyclic aromatic hydrocarbon (PAH), benzo(a)pyrene (BaP), a chemical carcinogen in cigarette smoke. Specifically, we hypothesized that cellular uptake and metabolism of BaP might be facilitated when the hydrocarbon was coated on asbestos. In addition, we were interested in whether asbestos, alone or in combination with BaP, caused single strand breakage of DNA in epithelial cells of the airway. UICC reference samples of crocidolite and chrysotile were coated with 3H-BaP before their addition to monolayers of hamster tracheal epithelial cells. In comparative studies, 3H-BaP at identical amounts was added to cells in culture medium. At intervals thereafter, uptake of BaP by cells was documented by scintillation spectrometry and by autoradiography. In addition, cells and media were assayed by use of high pressure liquid chromatography (HPLC) to demonstrate the water-soluble metabolites of BaP. The integrity of DNA was monitored by alkaline elution at intervals after exposure of tracheal cells to various concentrations of asbestos, BaP and BaP-coated asbestos. A rapid transfer of BaP to cells occurred after addition of BaP-coated asbestos to cultures. When BaP was adsorbed to both types of fibers before their addition to cultures, 70% of the total BaP introduced entered the cell within 1 hr; 50% remained intracellular after 8 hr. In contrast, if identical amounts of BaP were added directly to medium, an initial influx of 20% was observed and cells retained only 5% of the initial amount at 8 hr.(ABSTRACT TRUNCATED AT 250 WORDS)