An Evaluation Of The Mode Of Action (Moa) And Human Relevance Of Rat Liver Tumours Observed In A Chronic Rat Feeding Study With Silthiofam

Western blot analysis of microsomes and partially purified cytochrome P450 (CYP) from digestive gland of Mytilus edulis was carried out using polyclonal antibodies to hepatic Perca fluviatilis CYP1A, Oncorhynchus mykiss CYP3A and rat CYP2B, CYP2E and CYP4A isoforms. Multiple CYP bands were detected in partially purified CYP compared to single bands for microsomes for anti-CYP1A, anti-CYP2B, anti-CYP2E and anti-CYP3A. In contrast, anti-CYP4A showed two distinct bands for both. The apparent molecular weights in kD (mean±range or S.D.; n=2–4) for partially purified CYP were 42.5±0.5 and 48.1±0.3 (2 bands, anti-CYP1A); 67.4±0.7, 52.8±0.6, 44.5±2.5 (3 bands, anti-CYP3A); 52.8±0.7, 48.1±1.1 and 43.9±1.1 (3 bands, anti-CYP2B); 52.7±0.8 and 47.2±0.2 (2 bands, anti-CYP2E); 50.9±0.3 and 44.1±0.2 kD (2 bands, anti-CYP4A). Digestive gland microsomes of Mytilus galloprovincialis from a polluted compared to a clean field site showed higher levels of bands recognised by anti-CYP1A, anti-CYP2E and anti-CYP4A, but not anti-CYP2B and anti-CYP3A (P<0.05), indicative of independent regulation of different CYP forms. Overall, the apparent molecular weight and field studies indicate at least five different digestive gland CYP forms.