COMPARATIVE TIME-COURSE OF BENZO[A]PYRENE-DNA ADDUCT FORMATION, AND ITS RELATIONSHIP TO CYP1A ACTIVITY IN 2 SPECIES OF CATFISH

Studies have demonstrated differences between the brown bullhead (Amer iurus nebulosus) (BB) and a closely related species of catfish, the ch annel catfish (Ictalurus punctatus) (CC) in activity of important live r enzymes that may affect their ability to activate or detoxify, certa in procarcinogens. We have measured the formation and persistence of b enzo[a]pyrene-DNA adducts in the liver of these two species using the P-32-postlabeling (PPL) method, along with the effect of prior inducti on by beta-naphthoflavone (beta NF). In this time-course study, a tota l of 80 fish from each species were used. Half were induced with beta NF (i.p. injections of IO mg kg(-1) at day 3 and 2) followed by a sing le benzo[a]pyrene (BaP) i.p. injection (20 mg kg(-1)). Liver DNA and m icrosomes 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 tha n in BB. In contrast, the BaP-DNA adduct profile revealed a significan tly higher level of adducts in the BE than the CC. Adduct levels at mo st time points were significantly higher in the BE than in the CC at p <0.05. Further characterization of the major adduct by HPLC confirmed it to be the anti-BPDE-dG adduct. The adduct profiles of BaP are in c ontrast to what has been observed for adducts of 2-aminoanthracene in these species, although it is consistent with the relative species sus ceptibility to PAH induced liver neoplasia. (C) 1998 Elsevier Science Ltd. All rights reserved.