Schoepe K B, Friesel H, Schurdak M E, Randerath K, Hecker E
Carcinogenesis. 1986 Apr;7(4):535-40. doi: 10.1093/carcin/7.4.535.
The binding of some mouse skin metabolites and related derivatives of the tumor initiator 7,12-dimethylbenz[a]anthracene (DMBA) was investigated by 32P-postlabeling analysis after its topical administration. DMBA and trans-3,4-dihydro-3,4-dihydroxy-DMBA (DMBA-3,4-dihydrodiol) both led to the formation of four DNA adducts, which showed a very similar pattern of spots on thin-layer chromatograms. With trans-8,9-dihydro-8,9-dihydroxy-7,12-dimethylbenz[a]anthracene (DMBA-8,9-dihydrodiol) one major adduct was obtained which was chromatographically indistinguishable from one of the DMBA adducts. In contrast, 7-hydroxymethyl-12-methylbenz[a]anthracene (7-OHM-12-MBA) gave rise to two major adducts which were separable from DMBA adducts. 3-hydroxy-7,12-dimethylbenz[a]anthracene (3-OH-DMBA) and 7,12-dimethylbenz[a]anthracene-7,12-epoxide (DMBA-O2) did not lead to detectable amounts of adducts. Quantitative determination of DNA binding showed that an initiating dose (i = 100 nmol) of DMBA yielded approximately 12 adducts/10(7) normal nucleotides. Adduct formation with the same dose of DMBA-3,4-dihydrodiol was 7-8 times higher. At a 4-fold higher dose level, DMBA-8,9-dihydrodiol exhibited a 3- to 6-times weaker binding and 7-OHM-12-MBA a slightly stronger binding than DMBA. Chromatography of the DMBA and DMBA-3,4-dihydrodiol adducts with a solvent containing borate showed a decreased mobility of two out of four adducts in each case. These adducts were also sensitive to oxidation by periodate. The results suggest that two DMBA adducts carried vicinal cis-hydroxyl groups and thus were probably derived from the anti-3,4-dihydrodiol-1,2-oxide(s) of DMBA. The other two adducts were probably derived from the syn-stereoisomer(s). When the DNA-modifying capabilities and initiating activities of the more prominent mouse-skin metabolites are considered in relation to DMBA, DMBA-3,4-dihydrodiol is postulated to be a proximate and DMBA-3,4-dihydrodiol-1,2-oxide(s) to be ultimate initiators.
在局部应用肿瘤引发剂7,12-二甲基苯并[a]蒽（DMBA）后，通过³²P后标记分析研究了一些小鼠皮肤代谢产物及DMBA相关衍生物的结合情况。DMBA和反式-3,4-二氢-3,4-二羟基-DMBA（DMBA-3,4-二氢二醇）均导致形成四种DNA加合物，它们在薄层色谱图上显示出非常相似的斑点模式。反式-8,9-二氢-8,9-二羟基-7,12-二甲基苯并[a]蒽（DMBA-8,9-二氢二醇）得到一种主要加合物，其在色谱上与DMBA加合物之一无法区分。相比之下，7-羟甲基-12-甲基苯并[a]蒽（7-OHM-12-MBA）产生两种主要加合物，可与DMBA加合物分离。3-羟基-7,12-二甲基苯并[a]蒽（3-OH-DMBA）和7,12-二甲基苯并[a]蒽-7,12-环氧化物（DMBA-O₂）未导致可检测量的加合物。DNA结合的定量测定表明，起始剂量（i = 100 nmol）的DMBA产生约12个加合物/10⁷个正常核苷酸。相同剂量的DMBA-3,4-二氢二醇形成的加合物数量高7 - 8倍。在高4倍的剂量水平下，DMBA-8,9-二氢二醇的结合能力比DMBA弱3至6倍，而7-OHM-12-MBA的结合能力略强于DMBA。用含硼酸盐的溶剂对DMBA和DMBA-3,4-二氢二醇加合物进行色谱分析表明，每种情况下四种加合物中有两种的迁移率降低。这些加合物也对高碘酸盐氧化敏感。结果表明，两种DMBA加合物带有邻位顺式羟基，因此可能源自DMBA的反式-3,4-二氢二醇-1,2-环氧化物。另外两种加合物可能源自顺式立体异构体。当考虑更突出的小鼠皮肤代谢产物与DMBA相关的DNA修饰能力和引发活性时，推测DMBA-3,4-二氢二醇是直接引发剂，而DMBA-3,4-二氢二醇-1,2-环氧化物是最终引发剂。
