Effects of polycyclic aromatic hydrocarbons on expression of CYP1A in salmon (Salmo salar) following experimental exposure and after the Braer oil spill

The induction of hepatic CYP1A by selected polycyclic aromatic hydrocarbons (PAHs) was followed in Atlantic salmon (Salmo salar) by measurement of CYP1A messenger RNA (mRNA), CYP1A protein levels, and catalytically by the measurement of 7-ethoxyresorufin-O-deethylase activity. There was clear correspondence between all three methods of measurement both in terms of the specificity of response to five- and some four-ring PAHs and in terms of the dose-response relationship to methylcholanthrene. The level of induction was compared with that measured in salmon confined in sea pens around Shetland and exposed to crude oil spilled from the Braer in January 1993. This oil was rapidly dispersed by the extreme weather (turbulence) at the time of the spill. The time course of the hepatic CYP1A induction was followed and related to the levels of oil measured in water and the concentration of PAHs determined in the flesh of the fish. Again there was a good correspondence between the different methods of measuring CYP1A expression, and the results show a rapid induction response in fish at the most contaminated sites and small; insignificant changes occurring at the reference stations. There was a clear concentration response between CYP1A and catalytic activity and between the exposure observed.