The authors have investigated the formation of DNA adducts in starved, fed, and 5,6-benzoflavone-pretreated carp following i.p. administration of benzo(a)pyrene. (32)P-postlabeling analysis of the liver DNAs showed the presence of one predominant (>92%) adduct in all three groups. Cochromatography experiments revealed that the main adduct was identical to authentic BPDEI-dG (10(beta)-(deoxyguanosin-N2-yl)-7(beta), 8(alpha), 9(alpha)-trihydroxy-7,8,0,10-tetrahydrobenzo(a)pyrene). The formation of the adduct was evident as early as 1.5 h post-treatment and the levels increased steadily up to 7 days, reaching about 125, 110, and 102 attomole/microgram DNA in starved, fed, and benzoflavone-pretreated carp, respectively. During this period, the benzo(a)pyrene-induced benzo(a)pyrene monooxygenase activity increased from the uninduced, natural level of about 3 pmol/mg per min to levels of 35, 62, and 79 pmol/mg per min in starving, fed, and 5,6-benzoflavone pretreated fish, respectively. A slow but steady formation of the diolepoxide-dG adduct was also observed in the liver DNA of carp following p.o. treatment. (Copyright (c) 1991 Elsevier Scientific Publishers Ireland Ltd.)