Sindhu R K, Kikkawa Y
Department of Pathology, College of Medicine, University of California at Irvine 92717, USA.
Toxicol Lett. 1995 Nov;81(1):5-13. doi: 10.1016/0378-4274(95)03403-x.
Using a new sensitive reverse-phase HPLC assay with on-line radioactivity detector, metabolism of (+)-trans-benzo[a]pyrene-7,8-dihydrodiol (B[a]P diol) to the ultimate carcinogen benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE) was studied using 3-methylcholanthrene-induced rat liver homogenates. The results demonstrate that the stereoselectivity of B[a]PDE formation is a function of the concentration of the cellular constituents in the incubation media. At more dilute concentrations of the homogenate, the ratio of anti- to syn-B[a]PDE was the highest and decreased as the homogenate protein was increased in the incubation medium. However, there was a marked and parallel decrease of free B[a]PDE and DNA-bound radioactivity with increasing concentrations of cellular constituents in the incubation medium. The decreased DNA-bound radioactivity appears to be due to the preferential binding of B[a]PDE to glutathione and to proteins as the homogenate concentration was increased in the incubation media. These results indicate that liver homogenates, while apparently preserving the function of microsomes, present additional opportunities to study the interrelationship among cytochrome P450 monooxygenase activity, water-soluble conjugates, and binding of B[a]P diol metabolites to macromolecules in the study of benzo[a]pyrene-induced carcinogenesis.
使用一种带有在线放射性检测器的新型灵敏反相高效液相色谱法，利用经3-甲基胆蒽诱导的大鼠肝匀浆研究了(+)-反式苯并[a]芘-7,8-二氢二醇（B[a]P二醇）代谢生成最终致癌物苯并[a]芘-7,8-二醇-9,10-环氧化物（B[a]PDE）的过程。结果表明，B[a]PDE形成的立体选择性是孵育介质中细胞成分浓度的函数。在匀浆浓度较低时，反式B[a]PDE与顺式B[a]PDE的比例最高，且随着孵育介质中匀浆蛋白的增加而降低。然而，随着孵育介质中细胞成分浓度的增加，游离B[a]PDE和与DNA结合的放射性显著且平行下降。与DNA结合的放射性降低似乎是由于随着孵育介质中匀浆浓度的增加，B[a]PDE优先与谷胱甘肽和蛋白质结合。这些结果表明，肝匀浆在明显保留微粒体功能的同时，为研究苯并[a]芘诱导的致癌作用中细胞色素P450单加氧酶活性、水溶性结合物以及B[a]P二醇代谢物与大分子的结合之间的相互关系提供了更多机会。
