Elevated levels of multiple cytochrome P450 forms in tilapia from BillingsReservoir-Sao Paulo, Brazil

Cytochrome P4501A (CYP1A) levels in tissues of fish inhabiting polluted are as have been used extensively in biomonitoring studies in Europe and North America. However, little information is available about the extent of CYP1A expression in fish from South American waters, nor on the expression of ot her CYP proteins in fish from polluted sites. The content of total cytochro me P450 and b(5) and of proteins cross-reactive with antibodies to teleost (scup) CYP1A-, CYP2B- and CYP3A-like proteins, as well as rates of alkoxy-r esorufin-O-dealkylases (ARODs) with methoxy-, ethoxy-, pentoxy- and benzylo xyresorufin substrates, were analyzed in liver and kidney microsomes from t ilapia (Orcochromis niloticus) from a reference site (Estacao de Piscicultu ra de Pindamonhangaba, Sao Paulo) and a polluted site (Billings Reservoir, Sao Paulo, Brazil). Levels of total microsomal P450 and b(5) were elevated 1.8- and 3.3-fold, respectively, in liver and 4.3- and 2.4-fold in kidney o f tilapia from Billings Reservoir. Rates of all four ARODs and the levels o f CYP1A-, CYP2B- and CYP3A-cross-reactive proteins were elevated in liver a nd kidney of fish from Billings Reservoir compared to those in reference fi sh. Hepatic microsomal EROD and MROD were about 20-fold greater and levels of 1A protein more than 400-fold greater in Billings fish. Antibodies to te leost CYP1A and putative CYP3A recognized single bands while Pab to the scu p CYP2B-like protein recognized three protein bands in liver and kidney. Th is suggests that there are multiple CYP2B-like proteins expressed in tilapi a. Immunohistochemical analysis also indicated increased expression of CYP1 A cross-reactive proteins in cells of liver, gill, kidney and heart. The ap parent induction of CYP1A probably reflects the exposure to aryl hydrocarbo n receptor agonists present as pollutants in the Billings Reservoir. Elevat ed levels of the other CYP forms in tissues of tilapia from Billings Reserv oir could be related either to the presence of pollutants or to some natura l compound present in the diet, since tilapia is known as an herbivorous sp ecies. (C) 1999 Elsevier Science B,V. All rights reserved.