Weimer T L, Reddy A P, Harttig U, Alexander D, Stamm S C, Miller M R, Baird W, Hendricks J, Bailey G
Department of Pharmacology and Toxicology, West Virginia University, Morgantown, West Virginia 26506, USA.
Toxicol Sci. 2000 Oct;57(2):217-28. doi: 10.1093/toxsci/57.2.217.
Metabolism, DNA adduction, and tumor induction by 7, 12-dimethylbenz(a)anthracene (DMBA) were examined in cultured trout liver cells and in vivo in trout. Modulating CYP1A1 activity indicated this enzyme plays a significant role in metabolizing DMBA to water-soluble compounds in isolated trout liver cells. The major DMBA metabolites identified in trout liver cells were 10-, 11-, 8,9-, and 5,6-DMBA dihydrodiols, and DMBA, 2- or 3- or 4-phenol; 7-OH-methyl-12-methyl-benz(a)anthracene and 12-OH-methyl-7-methyl-benz(a)anthracene were minor metabolites. A very small amount of DMBA-3,4-dihydrodiol was detected, and polar metabolites, which did not migrate with any DMBA metabolite standards, were observed. Incubating trout hepatocytes with DMBA-3, 4-dihydrodiol produced three prominent, nonpolar adducts indistinguishable from those in mouse embryo cells. However, DMBA-DNA adducts, formed in trout in vivo or in trout liver cells exposed to DMBA, were predominantly more polar than those formed in mouse embryo fibroblasts, and levels of DMBA-DNA adducts formed in trout liver cells were not significantly altered by modulating CYP1A1 activity. No significant repair of DMBA-DNA adducts was detected in cultured trout liver cells over a 48-h period, supporting previous studies indicating that fish are less efficient than mammals in repairing polyaromatic hydrocarbon DNA adducts. Compared to animals receiving DMBA alone, beta-naphthoflavone pretreatment in vivo did not affect hepatic CYP1A1, DMBA-DNA adducts, nor hepatic tumor response; but did significantly reduce tumor response in two other target organs. These results collectively indicate that DMBA bioactivation to DNA-binding metabolites in trout liver cells and mouse embryo cells predominantly involve different metabolic pathways to form the DNA-binding intermediates.
在培养的鳟鱼肝细胞和鳟鱼体内研究了7,12 - 二甲基苯并(a)蒽（DMBA）的代谢、DNA加合物形成及肿瘤诱导情况。调节CYP1A1活性表明，该酶在将DMBA代谢为分离的鳟鱼肝细胞中的水溶性化合物过程中起重要作用。在鳟鱼肝细胞中鉴定出的主要DMBA代谢产物为10 -、11 -、8,9 - 和5,6 - DMBA二氢二醇，以及DMBA、2 - 或3 - 或4 - 苯酚；7 - 羟基甲基 - 12 - 甲基苯并(a)蒽和12 - 羟基甲基 - 7 - 甲基苯并(a)蒽是次要代谢产物。检测到极少量的DMBA - 3,4 - 二氢二醇，并观察到一些极性代谢产物，它们在与任何DMBA代谢产物标准品的迁移情况不同。用DMBA - 3,4 - 二氢二醇孵育鳟鱼肝细胞产生了三种突出的非极性加合物，与小鼠胚胎细胞中的加合物无法区分。然而，在鳟鱼体内或暴露于DMBA的鳟鱼肝细胞中形成的DMBA - DNA加合物，主要比在小鼠胚胎成纤维细胞中形成的加合物极性更强，并且通过调节CYP1A1活性，鳟鱼肝细胞中形成的DMBA - DNA加合物水平没有显著改变。在48小时内，培养的鳟鱼肝细胞中未检测到DMBA - DNA加合物的显著修复，这支持了先前的研究，即鱼类在修复多环芳烃DNA加合物方面比哺乳动物效率更低。与单独接受DMBA的动物相比，体内β - 萘黄酮预处理不影响肝脏CYP1A1、DMBA - DNA加合物或肝脏肿瘤反应；但确实显著降低了另外两个靶器官的肿瘤反应。这些结果共同表明，DMBA在鳟鱼肝细胞和小鼠胚胎细胞中生物活化形成DNA结合代谢产物主要涉及不同的代谢途径来形成DNA结合中间体。
