title: The liver monooxygenase system of Brazilian freshwater fish.
abstract: Content of cytochromes b5 and P-450, and activities of NADPH-cytochrome c (P-450) reductase (NCR) and 7-ethoxyresorufin O-deethylase (EROD) were measured in liver microsomes prepared from two South American endemic fish, Brycon cephalus and Colossoma macropomum, from tilapia, Oreochromis niloticus, and from Swiss mice, Mus musculus, which served as a control. Strong hemoglobin binding to fish liver microsomal membranes (FLM) altered visible spectra of microsomal cytochromes. Consequently, special precautions during FLM preparation, including liver perfusion followed by repeated washing of microsomes, were required in the study of microsomal cytochromes from these fish. FLM from all fish studied here had a significantly lower content of microsomal cytochromes but a similar level of NCR and EROD activities compared to mouse liver microsomes (MLM). Strong response of the monooxygenase system in O. niloticus to water pollution was detected with both specific cytochrome P-450 content and EROD activity increasing sharply. The optical spectra of hemoglobin from B. cephalus and C. macropomum were analyzed and some differences in shape and relative extinction were observed compared to known hemoglobins.
authors.affiliation: Department of Biochemistry, University of São Paulo, Brazil.
authors.forename: M A
authors.initials: MA
authors.lastname: Leitão
authors.forename: E G
authors.initials: EG
authors.lastname: Affonso
authors.forename: M F
authors.initials: MF
authors.lastname: da Silva
authors.forename: N C
authors.initials: NC
authors.lastname: Meirelles
authors.forename: F T
authors.initials: FT
authors.lastname: Rantin
authors.forename: A E
authors.initials: AE
authors.lastname: Vercesi
authors.forename: V B
authors.initials: VB
authors.lastname: Junqueira
authors.forename: I A
authors.initials: IA
authors.lastname: Degterev
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis*; D015786:Cytochromes b5 / Q000096:biosynthesis*; D004790:Enzyme Induction / Q000187:drug effects; D005399:Fishes / Q000502:physiology*; D007425:Intracellular Membranes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000096:biosynthesis*; D017210:Tilapia; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D015786:Cytochromes b5; D019363:Cytochrome P-450 CYP1A1; D009251:NADPH-Ferrihemoprotein Reductase