Cytochrome P4501A induction and porphyrin accumulation in PLHC-1 fish cells exposed to sediment and oil shale extracts

The present study describes the use of a fish hepatoma cell Line (PLHC-1) i n monitoring the biological effects of sediments collected from recipient w aters of the oil shale industry. Sampling sites were located in River Purts e and River Kohtla in northeast Estonia. The effects of pure oil shale on t he PLHC-1 cells were also studied. The cells were exposed to n-hexane-extra cted samples in 48-well plates for 24 h, and 7-ethoxyresorufin O-deethylase (EROD) activity, total protein, and porphyrin content were measured in the exposed cells. Polycyclic aromatic hydrocarbon (PAH) contents in the sampl es were measured by high-performance Liquid chromatography (HPLC). All the sediment and oil shale samples induced CYP1A activity and led to porphyrin accumulation in the cells. The most potent inducers were the sediments coll ected near the oil shale processing plants (site Luganuse in River Purtse a nd Kohtla in River Kohtla), as well as those at the most downstream site in River Purtse (Purtse). These samples possessed high total PAH contents, ra nging from 4,270 to nearly 150,000 mu g/kg dry sediment. The presence of ot her lipophilic organic contaminants in the samples was not determined in th is study. Both EROD activity and porphyrin content exhibited biphasic induc tion curves, and the ED501 values for EROD activity were lower than the ED( 50)s for porphyrin content. 2,3,7,8-Tetrachlorodibenzo-p-dioxin induction e quivalents (TCDD-EQs) calculated from EROD induction potencies correlated w ell with total PAHs (r(2) = 0.827 and p = 0.003 for log-transformed data) a nd also with individual PAHs. TCDD-EQs for porphyrin content did not correl ate significantly with total PAHs (log-log r(2) = 0.785, p = 0.116). The bi ological potency and PAH contamination of the samples showed the same rank order, except at Luganuse, where sediment extracts induced CYP1A and porphy rins more than could have been expected based on PAH contents. Bioassay-der ived induction EQs (normalized to dibenz(a,h)anthracene) were 20- to 3,200- fold greater than EQs calculated from the concentrations of five PAHs, sugg esting important contributions from other compounds or nonadditive effects. The PLHC-1 cells proved to be a sensitive bioanalytical tool for sediments contaminated with PAM-type pollutants in the oil shale processing area. We suggest further use of this bioassay in screening and monitoring waters wi th similar background of pollution as in northeast Estonia.