The effects of temperature on benzo[a]pyrene metabolism and adduct formation in the gulf toadfish,Opsanus beta

Abstract

In order to examine the effects of temperature on benzo[a]pyrene (BaP) metabolism and adduct formation in the absence of the effects of temperature on uptake, gulf toadfish,Opsanus beta, were given a dose of 0.05 mg/kg(3)H-BaPvia caudal vein cannulae at their acclimation temperatures. (18 or 28°C) or following an acute temperature change (18 to 28°C or 28 to 18°C). After 72h, BaP-derived radioactivity was detected in all tissues examined and, as in otherin vivo studies of fish, the highest levels were found in the bile, the liver and the kidney. Temperature did not affect the total amount of BaP metabolized and excreted to the bile, but there were significant quantitative differences between temperature treatments in the classes of Phase I metabolites accumulated. Fish acclimated to high temperature accumulated more BaP triols and tetrols (breakdown products of highly carcinogenic BaP diol epoxides) than fish acclimated at low temperature regardless of exposure temperature: the proportion of biliary metabolites as tetrols and triols in each of the four temperature treatments (acclimation: exposure temperature), 28:18, 28:28, 18:18 and 18:28°C were 21.3±3.6, 58.1±6.1, 14.2±1.8 and 20.9±3.2% (mean±SEM, n=4), respectively. Significant quantities of BaP-DNA and BaP-hemoglobin adducts were detected; however, only the amounts of BaP-DNA adducts showed sensitivity to temperature. As predicted from our metabolite data, high acclimation or exposure temperature led to a significant increase in the amount of BaP-DNA adducts formed: adduct formation in the temperature treatments, 28:18, 28:28, 18:18 and 18:28°C were 342±52, 526±51, 155±42 and 252±55 fg BaP/ µg DNA (mean±SEM, n=4), respectively. These results are discussed in the context of mechanisms of high temperature-enhancement of carcinogenesis in fish.