In vitro biotransformation of organohalogens by sperm whale microsomes in relation to the CYP-isozymes present

Microsomes were isolated from three male sperm whales stranded alive on the coasts of the Netherlands or Denmark. Iso-enzymes of cytochrome P450 were characterized immunochemically by Western Blotting. All three animals showed bands of CYP1A, CYP3A and CYP4A, but CYP2B was lacking. The microsomes of the sperm whales were able to metabolize 4,4′-dichlorobiphenyl (CB-15), 2,7 dichloro-p-dibenzodioxin, and 1,2,3,7,8 pentachlorodibenzofuran. In contrast, 3,3′,4,4′-tetrachlorobiphenyl (CB-77), four individual chlorobornanes (CHBs) and three polybrominated diphenylethers (PBDEs) were persistent in the in vitro assays. Microsomes of a harbour seal were able to metabolize the same compounds as the sperm whale microsomes, but CB-77 and two individual CHBs (CHB-32 and CHB-62) were also metabolized. In addition to the bands identified in the sperm whales, harbour seal microsomes also showed clear bands of CYP2B.