Huang P H, Catalano A
Foundation 41, East Sydney, N.S.W., Australia.
Teratog Carcinog Mutagen. 1994;14(2):53-64. doi: 10.1002/tcm.1770140202.
1,2-Diethylhydrazine (DEH) and dimethylnitrosamine (DMN) are indirect acting carcinogens that require metabolic activation to exert their potency. DEH is a transplacental carcinogen and teratogen in Wistar rats when administered by i.p. injection on day 12 of gestation. DMN is embryotoxic during this period. In this study, gravid Wistar rats were injected i.v. with DEH (10, 15, or 20 mg/kg) or i.p. with DMN (10 or 30 mg/kg) and the effects on the embryos 24 hours later were observed. Controls were similarly injected with saline vehicle. The incidence of resorptions increased after treatment with 20 mg DEH/kg. DEH treatment also resulted in decreases in embryo wet weights and total DNA that were not dose dependent. Treatment with DMN did not affect embryonic wet weights and total embryonic DNA amount when compared to the saline-treated controls. The effects of DEH and DMN on DNA synthesis in vivo were monitored by injecting [methyl-14C]-thymidine 1 hour prior to embryo death. DEH induced significant increases in thymidine incorporation into embryo DNA but the increases were not proportional to the doses administered. DNA synthesis was significantly decreased in embryos treated with 30 mg DMN/kg. The DNA of treated and control embryos was fractionated by benzoylated DEAE-cellulose (BD-cellulose) chromatography to determine differences in DNA secondary structure following treatment. BD-cellulose chromatography separates double-stranded DNA from DNA containing single-stranded regions by step elution with 1 M NaCl solution and caffeine solution, respectively. Embryonic DNA was monitored by in vivo labelling with [methyl-3H]-thymidine on days 6 and 7 of gestation. Significant dose dependent increases in percentages of caffeine-eluted DNA (%CE-DNA) compared to controls were detected after treatment with 10, 15, and 20 mg DEH/kg and 10 and 30 mg DMN/kg. The relative %CE-DNA is expressed as the ratio of %CE-14C-labeled DNA to %CE-3H-labeled DNA. Litters treated with 10, 15, and 20 mg DEH/kg had relative %CE-DNA values significantly lower than controls. The results support the hypothesis that initiation mechanisms of transplacental carcinogenesis and teratogenesis are different. The pertinence of %CE-DNA and relative %CE-DNA values to the study of transplacental carcinogenesis and teratogenesis is discussed.
1,2 - 二乙肼（DEH）和二甲基亚硝胺（DMN）是间接作用致癌物，需要代谢激活才能发挥其致癌作用。DEH在妊娠第12天经腹腔注射时，对Wistar大鼠是一种经胎盘致癌物和致畸物。在此期间，DMN具有胚胎毒性。在本研究中，对妊娠的Wistar大鼠静脉注射DEH（10、15或20 mg/kg）或腹腔注射DMN（10或30 mg/kg），并观察24小时后对胚胎的影响。对照组同样注射生理盐水。用20 mg DEH/kg处理后，吸收的发生率增加。DEH处理还导致胚胎湿重和总DNA减少，但与剂量无关。与生理盐水处理的对照组相比，DMN处理对胚胎湿重和总胚胎DNA量没有影响。在胚胎死亡前1小时注射[甲基 - 14C] - 胸苷，监测DEH和DMN对体内DNA合成的影响。DEH诱导胸苷掺入胚胎DNA显著增加，但增加与给药剂量不成比例。用30 mg DMN/kg处理的胚胎中DNA合成显著减少。用苯甲酰化DEAE - 纤维素（BD - 纤维素）色谱法分离处理组和对照组胚胎的DNA，以确定处理后DNA二级结构的差异。BD - 纤维素色谱法分别用1 M NaCl溶液和咖啡因溶液分步洗脱，将双链DNA与含有单链区域的DNA分离。在妊娠第6天和第7天用[甲基 - 3H] - 胸苷体内标记监测胚胎DNA。用10、15和20 mg DEH/kg以及10和30 mg DMN/kg处理后，与对照组相比，咖啡因洗脱DNA百分比（%CE - DNA）出现显著的剂量依赖性增加。相对%CE - DNA表示为%CE - 14C标记DNA与%CE - 3H标记DNA的比值。用10、15和20 mg DEH/kg处理的窝仔相对%CE - DNA值显著低于对照组。结果支持经胎盘致癌和致畸的起始机制不同这一假说。讨论了%CE - DNA和相对%CE - DNA值在经胎盘致癌和致畸研究中的相关性。
