Immunochemical detection of cytochrome P450IA1 induction in cod larvae and juveniles exposed to a water soluble fraction of North Sea crude oil

Using a flow-through biotest exposure system, cod eggs, larvae and juveniles were exposed to the water-soluble fraction (WSF) of North Sea (Statfjord B) crude oil at concentrations ranging from 40–300 μg l −1 (ppb) for 1–6 weeks. The WSF was analysed by GC/MS, and was shown to be dominated by low-aromatic compounds such as benzenes, toluene and xylenes (80–90%). Cytochrome P450IA1 levels were measured by immunochemical techniques in 10 000 × g supernatants of whole larvae or juvenile gill homogenates, and in juvenile liver microsomal fractions. With rabbit anti-cod P450IA1 IgG as primary antibody in an indirect ELISA, a clear induction response was observed in the exposed groups of both larvae and juveniles. The response was dose-dependent, and recovery in clean sea-water resulted in normalization of the induced P450IA1 levels. In larvae exposed during the egg stage, the induction process seemed restricted until the time of hatching. In juvenile cod, the response was observed in the gill in addition to the liver. The study demonstrates the usefulness of the cytochrome P450IA1 ELISA in detecting sublethal biological effects of pollutants in small sample sizes where enzyme activity is difficult to measure.