R. Todorovic et al., DETERMINATION OF BENZO[A]PYRENE-DNA AND 7,12-DIMETHYLBENZ[A]ANTHRACENE-DNA ADDUCTS FORMED IN RAT MAMMARY-GLANDS, Chemical research in toxicology, 10(9), 1997, pp. 941-947
Both 7,12-dimethylbenz[a]anthracene (DMBA) and benzo[a]pyrene (BP) are
carcinogenic in the rat mammary gland. The depurinating and stable ad
ducts of DMBA and BP formed in vitro and in mouse skin were previously
identified and quantitated. Identification and quantitation of the de
purinating and stable DNA adducts of DMBA and identification of the de
purinating adducts of BP formed in rat mammary glands in the 24 h afte
r intramammillary injection of DMBA or BP are reported in this paper.
The depurinating adducts of DMBA, which constitute 52% of all adducts
detected, are DMBA bound at the 12-methyl group to the N-7 of adenine
(Ade) or guanine (Gua), namely, 7-methylbenz[a]anthracene (MBA)-12-CH2
-N7Ade (39%) and 7-MBA-12-CH2-N7Gua (13%). All of the stable adducts w
ere formed from the diol epoxide(s) of DMBA. Depurinating adducts of B
P with guanine, namely, 8-(BP-6-yl)-guanine (BP-6-C8Gua) and BP-6-N7Gu
a, were identified in rat mammary glands treated with BP. The major st
able adduct, formed via the diol epoxide pathway, BP-diol epoxide-10-N
(2)dG, accounted for over 64% of all the stable adducts. Three other B
P-DNA stable adducts remain unidentified. Thus, rat mammary cells form
depurinating adducts of DMBA and BP predominantly via their radical c
ations and stable adducts via the diol epoxides.