Thermal modulation of benzo[ a]pyrene metabolism by the gulf toadfish, Opsanus beta

Abstract

Gulf toadfish, Opsanus beta, were exposed to initial [ 14 C] benzo[a] pyrene (BaP) concentrations of 5 μg 1 −1 at acclimation temperatures (18 or 28°C) or following an acute temperature change (18 to 28°C or 28 to 18°C) in a simple static exposure system. At 24 h, fish were sacrificed and the bile was analyzed by HPLC for Phase I and Phase II metabolites of BaP. Toadfish can metabolize BaP rapidly, as very low levels of parent compound were detected, and the overall rate of uptake and metabolic processing of [ 14C]BaP was higher in fish exposed at high temperatures. There were no significant differences between temperature treatments in the proportions of organic soluble and aqueous soluble metabolites, which contributed approximately 7.8 and 92%, respectively. A variety of Phase I metabolites were produced by toadfish, and the major Phase I metabolite identified was benzo[ a]pyrene 7,8-dihydrodiol. There were significant quantitative differences between temperature treatments in the classes of Phase I metabolites produced. Fish acclimated to high temperature produced more triols and tetrols (breakdown products of highly carcinogenic BaP diol epoxides) than did fish acclimated at low temperature regardless of exposure temperature. Thus, in addition to increasing rate of uptake, higher temperatures appear to lead to a shift in metabolism towards potentially more carcinogenic intermediates.