NONGENOTOXIC EFFECTS OF POLYCYCLIC AROMATIC-HYDROCARBONS AND THEIR OZONATION BY-PRODUCTS ON THE INTERCELLULAR COMMUNICATION OF RAT-LIVER EPITHELIAL-CELLS

Since polycyclic aromatic hydrocarbons (PAHs) are known to have epigen etic effects, we evaluated the effect of the parent chemical and the o zonated products on in vitro cell to cell communication bioassays whic h measures a nongenotoxic event. The scrape loading/dye transfer (SL/D T) technique was used to determine the effect of the following PAHs on gap-junction intercellular communication (GJIC): fluorene, 1-methyl-f luorene, fluoranthene, anthracene, 9-methyl-anthracene, phenanthrene, pyrene, benzo(a)pyrene, and benzo(e)pyrene. The methylated PAHs were m ore inhibitory to GJIC than the unmethylated counterparts. Fluoranthen e, which has an additional ring added to fluorene, was more effective in inhibiting GJIC than fluorene. The three-ringed PAHs were also more inhibitory than the four- and five-ringed PAHs. A time-course study o f fluoranthene and of pyrene resulted in maximal inhibition occurring within 30 min of incubation with the cells. The cells recovered from t he inhibition within 1 hr after fluoranthene and pyrene were removed f rom the cell culture medium. Pyrene, benzo(a)pyrene; fluorene, and flu oranthene were ozonated until the parent compound was completely elimi nated as determined by reverse-phase high-pressure liquid chromatograp hy (RP-HPLC). An increased level of inhibition of GJIC was observed fo r the ozonated mixtures of by-products of pyrene, fluoranthene, and be nzo(a)pyrene, but not for fluorene, as monitored with the SL/DT techni que. The products of the ozonated pyrene mixture were fractionated and collected by RP-HPLC. Each fraction was found to be inhibitory to GJI C as monitored by fluorescence recovery after photobleaching. In concl usion, current treatment technologies, such as ozonation or biological ly based oxidations and methylations, do not necessarily eliminate tox icity. Therefore, it is imperative that toxicological studies be used to complement traditional chemical detection techniques used to monito r the fate of a pollutant in environmental treatment systems. (C) 1994 Society of Toxicology.