Alterations in hepatic mixed-function oxidase activity of rainbow trout after acute treatment with polybrominated biphenyl isomers and FireMaster BP-6.
The effects of FireMaster BP-6 and several pure isomers on hepatic microsomal mixed-function oxidase (MFO) activity in rainbow trout have been investigated. After one parenteral injection of these agents at 150 mg/kg and sacrifice 5 d later, there was no elevation of hepatic cytochrome P-450. The noncoplanar isomers 2,4,5,2',4',5'-hexa and 2,3,4,5,2',4',5'-heptabromobiphenyl did not increase any MFO activity generally associated with an increase in cytochrome P-450 levels, including the dealkylations of ethoxycoumarin and benzphetamine. The coplanar isomer 3,4,5,3',4',5'-hexabromobiphenyl produced an increase in O-deethylation of both ethoxycoumarin and ethoxyresorufin, suggesting enhancement of cytochrome P-448 associated activity, but produced no increase in benzphetamine N-dealkylation. The "mixed inducer" 2,4,5,3',4',5'-hexabromobiphenyl, produced a small but insignificant elevation of cytochrome P-448 associated MFO activities and no increase in cytochrome P-450 associated activities. At both 150 and 500 mg/kg, the commercial mixture of polybrominated biphenyls FireMaster BP-6 produced marked elevations of both ethoxycoumarin and ethoxy-resorufin dealkylations but had no effect on demethylation of benzphetamine. When microsomes from rainbow trout treated with FireMaster BP-6 were examined electrophoretically, A coomassie Blue-staining band at 57,000 daltons was intensified, as seen after treatment of fish with the cytochrome P-448 inducer beta-naphthoflavone. It is concluded that coplanar polybrominated isomers produce an induction of hepatic cytochrome P-448 associated activity, while noncoplanar isomers are ineffective as inducers of cytochrome P-450 related MFO activities in rainbow trout.
D000818:Animals; D001713:Biphenyl Compounds / Q000633:toxicity*; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D004790:Enzyme Induction; D005393:Fish Diseases / Q000139:chemically induced; D005411:Flame Retardants / Q000633:toxicity*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000096:biosynthesis*; D010088:Oxidoreductases / Q000096:biosynthesis*; D011075:Polybrominated Biphenyls / Q000633:toxicity*; D012487:Salmonidae / Q000378:metabolism*; D013237:Stereoisomerism; D014337:Trout / Q000378:metabolism*
D001713:Biphenyl Compounds; D005411:Flame Retardants; D011075:Polybrominated Biphenyls; C015885:Firemaster BP-6; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases