INCREASED CYP1A1 AND RIBOSOMAL-PROTEIN L5 GENE-EXPRESSION IN A TELEOST - THE RESPONSE OF JUVENILE CHINOOK SALMON TO COAL-DUST EXPOSURE

Molecular studies on the sublethal physiological effects of coal dust exposure in vertebrates are sparse. Coal dust contamination of the mar ine environment occurs, for example, around coal loading and storage t erminal. To determine the potential impact of coal dust exposure on ju venile chinook salmon, fish were exposed for an 8 day period to 60 mg L-1, 200 mg L-1 or 500 mg L-1 of coal dust in sea water and the levels of CYP1A1 mRNA quantitated using RT-cPCR. Two control groups were uti lized; one 'negative' control group was maintained in sea water only, whilst the second 'positive' control group was i.p. injected with beta -naphthoflavone (BNF: 50 mg kg(-1)). There was a significant increase in CYP1A1 expression in fish exposed to coal dust (ANOVA; P < 0.001), and in fish injected with BNF (t-test; P < 0.001), relative to control s. In addition, RT-PCR analysis indicated increased expression of a se cond gene in the fish exposed to coal dust. Sequence analysis identifi ed the second coal-dust-inducible gene as ribosomal protein L5. Both o f these genes, CYP1A1 and L5, encode proteins vital in cellular metabo lism. The enzyme encoded by CYP1A1 (P4501A1) plays an important role i n the metabolic activation of PAHs to carcinogenic and mutagenic metab olites. L5 plays a crucial role in ribosome biogenesis. At present, th e significance of the increased hepatic expression of L5 in coal dust exposed fish is unclear and warrants further investigation.