Comparative time-course of benzo[a]pyrene-DNA adduct formation, and its relationship to CYP1A activity in two species of catfish

Abstract Studies have demonstrated differences between the brown bullhead ( Ameriurus nebulosus ) (BB) and a closely related species of catfish, the channel catfish ( Ictalurus punctatus ) (CC) in activity of important liver enzymes that may affect their ability to activate or detoxify certain procarcinogens. We have measured the formation and persistence of benzof[ a ]pyrene-DNA adducts in the liver of these two species using the 32 P-postlabeling (PPL) method, along with the effect of prior induction by β-naphthoflavone (βNF). In this time-course study, a total of 80 fish from each species were used. Half were induced with βNF (i.p. injections of 10 mgkg −1 at day 3 and 2) followed by a single benzo[ a ]pyrene (BaP) i.p. injection (20 mg kg −1 ). Liver DNA and microsomes were sampled on day 1, 3, 7, 14 and 45 after the BaP dosage—adducts and ethoxyresorufin- O -deethylase (EROD) activity were analyzed. EROD activity in CC was significantly higher at most time points than in BB. In contrast, the BaP-DNA adduct profile revealed a significantly higher level of adducts in the BB than the CC. Adduct levels at most time points were significantly higher in the BB than in the CC at p