TOXICOLOGICAL AND ECOLOGICAL IMPLICATIONS OF BIOTRANSFORMATION ENZYMES IN THE TROPICAL TELEOST CHAETODON CAPISTRATUS

Hepatic cytochromes P450 (phase I monooxygenases) and glutathione tran sferases (phase II conjugating enzymes) were investigated in Chaetodon capistratus (Linnaeus) collected in Florida and Belize in June and De cember 1991, respectively. These biotransformation enzymes play major roles in the detoxification of xenobiotics by converting lipophilic ch emicals to more hydrophilic, readily excretable metabolites. Content o f total microsomal P450 (0.501 to 0.821 nmol mg(-1) microsomal protein ) and rates of NADPH-cytochrome c (P450) reductase (270.7 to 330.2 nmo l min(-1) mg(-1) microsomal protein) and glutathione transferase (2.81 to 3.12 mu g min(-1) mg(-1) cytosolic protein) in these fish were gre ater than in most untreated fish species, i.e., fish that have not bee n exposed to PAHs (polycyclic aromatic hydrocarbons) or PCBs (polycycl ic biphenyls). Ethoxyresorufin O-deethylase (EROD) rates (0.029 to 0.1 71 nmol min(-1) mg(-1)) were also comparable to those in most untreate d marine fish. Immunoblot analysis with monoclonal antibody (MAb) 1-12 -3 to scup P450E (the EROD catalyst and a teleost representative of th e PAH-inducible CYP1A gene subfamily) showed slight amounts of cross-r eacting protein in C. capiskratus liver microsomes. Hepatic CYP1A cont ent and EROD activity did not differ significantly between fish collec ted in Florida and Belize, suggesting that the two sites differed litt le in contamination by CYP1A inducers. Immunochemical analyses with po lyclonal antibodies to scup P450B (a teleost representative of the CYP 2B subfamily) and human CYP3A4 cross-reacted strongly with C. capistra tus hepatic proteins. The CYP2B and CYP3A subfamilies in mammals are b elieved to have partially evolved in response to toxic dietary alleloc hemicals. C. capistratus regularly feeds on terpenoid-rich gorgonian c orals, suggesting that biotransformation enzymes may be involved in th e metabolism of dietary allelochemicals as well as anthropogenic xenob iotics in this species.