Blakey D C, White I N
Carcinogenesis. 1985 Aug;6(8):1201-5. doi: 10.1093/carcin/6.8.1201.
The genotoxic potential of oral contraceptive steroids such as norethindrone was investigated in short-term rat hepatocyte cultures by measurement of unscheduled DNA synthesis. Norethindrone caused a small dose-dependent increase in unscheduled DNA synthesis in male rat hepatocytes as judged by the incorporation of [methyl-3H]thymidine into DNA. This was assessed either by liquid scintillation counting following isolation of DNA or by autoradiography. No increase in unscheduled DNA synthesis could be detected in female rat hepatocytes treated with norethindrone. Pre-treatment of male rats with phenobarbitone prior to hepatocyte preparation decreased the norethindrone mediated unscheduled DNA synthesis relative to control hepatocyte cultures while 3-methylcholanthrene pre-treatment had little effect. Unscheduled DNA synthesis in norethindrone treated control male rat hepatocytes was reduced by the mixed function oxidase inhibitors SKF 525A or metyrapone. In 24- or 52-hour-old hepatocyte cultures in which the cytochrome P-450 content was lower than in freshly prepared cells, or in a hepatocyte-derived cell line lacking cytochrome P-450, unscheduled DNA synthesis due to norethindrone was either decreased or abolished. Structure activity studies showed that only steroids containing a 17 alpha-ethynyl substituent caused an increase in unscheduled DNA synthesis.
通过测量非预定DNA合成，在短期大鼠肝细胞培养物中研究了炔诺酮等口服避孕药类固醇的遗传毒性潜力。通过将[甲基-3H]胸苷掺入DNA来判断，炔诺酮导致雄性大鼠肝细胞中非预定DNA合成出现小剂量依赖性增加。这可通过分离DNA后的液体闪烁计数或放射自显影进行评估。在用炔诺酮处理的雌性大鼠肝细胞中未检测到非预定DNA合成增加。在制备肝细胞之前用苯巴比妥预处理雄性大鼠，相对于对照肝细胞培养物，可降低炔诺酮介导的非预定DNA合成，而用3-甲基胆蒽预处理则影响不大。炔诺酮处理的对照雄性大鼠肝细胞中的非预定DNA合成可被混合功能氧化酶抑制剂SKF 525A或美替拉酮降低。在细胞色素P-450含量低于新鲜制备细胞的24或52小时龄肝细胞培养物中，或在缺乏细胞色素P-450的肝细胞衍生细胞系中，炔诺酮引起的非预定DNA合成要么减少要么消除。构效关系研究表明，只有含有17α-乙炔基取代基的类固醇会导致非预定DNA合成增加。
