Akagi Jun-Ichi, Toyoda Takeshi, Cho Young-Man, Mizuta Yasuko, Nohmi Takehiko, Nishikawa Akiyoshi, Ogawa Kumiko
Division of Pathology, National Institute of Health Sciences, Tokyo, Japan.
Biological Safety Research Center, National Institute of Health Sciences, Tokyo, Japan.
Cancer Sci. 2015 May;106(5):529-41. doi: 10.1111/cas.12634. Epub 2015 Apr 10.
Transgenic rodents carrying reporter genes to detect organ-specific in vivo genetic alterations are useful for risk assessment of genotoxicity that causes cancer. Thus, the Organization for Economic Co-operation and Development has established the guideline for genotoxicity tests using transgenic animals, which may be combined with repeated-dose toxicity studies. Here, we provide evidence to support equivalence of gpt delta and wild type (WT) rats in terms of toxicological responses to a genotoxic hepatocarcinogen, N-nitrosodiethylamine (DEN), and a non-genotoxic hepatocarcinogen, di(2-ethylhexyl)phthalate (DEHP). gpt delta rats treated with DEHP showed similar increases in liver and kidney weights, serum albumin, albumin/globulin ratios, and incidence of diffuse hepatocyte hypertrophy compared to WT F344 and Sprague-Dawley (SD) rats. DEN-treated gpt delta rats showed equivalent increases in the number and area of precancerous GST-P-positive foci in the liver compared to WT rats. The livers of DEN-treated gpt delta rats also showed increased frequencies of gpt and Spi(-) mutations; such changes were not observed in DEHP-treated gpt delta rats. These results indicated that gpt delta rats (both F344 and SD backgrounds) showed comparable DEHP-induced toxicity and DEN-induced genotoxicity to those observed in WT rats. With regard to the administration period, the general toxicity of 1.2% DEHP was evident throughout the experimental period, and the genotoxicity of 10 p.p.m. DEN could be detected after 2 weeks of administration and further increased at 4 weeks. These results suggested that combined assays using gpt delta rats could detect both general toxicity and genotoxicity by the canonical 4-week administration protocol. Therefore, this assay using gpt delta rats would be applicable for risk assessment including early detection of genotoxic carcinogens and ultimately serve to reduce cancer risks in humans from environmental chemicals.
携带报告基因以检测体内器官特异性基因改变的转基因啮齿动物，对于导致癌症的遗传毒性风险评估很有用。因此，经济合作与发展组织已经制定了使用转基因动物进行遗传毒性测试的指南，该测试可与重复剂量毒性研究相结合。在此，我们提供证据支持gpt delta大鼠和野生型（WT）大鼠在对遗传毒性肝癌致癌物N-亚硝基二乙胺（DEN）和非遗传毒性肝癌致癌物邻苯二甲酸二（2-乙基己基）酯（DEHP）的毒理学反应方面具有等效性。与WT F344和Sprague-Dawley（SD）大鼠相比，用DEHP处理的gpt delta大鼠在肝脏和肾脏重量、血清白蛋白、白蛋白/球蛋白比率以及弥漫性肝细胞肥大发生率方面表现出相似的增加。与WT大鼠相比，用DEN处理的gpt delta大鼠肝脏中癌前GST-P阳性灶的数量和面积增加相当。用DEN处理的gpt delta大鼠的肝脏中gpt和Spi(-)突变频率也增加；在用DEHP处理的gpt delta大鼠中未观察到此类变化。这些结果表明，gpt delta大鼠（F344和SD背景）对DEHP诱导的毒性和DEN诱导的遗传毒性与WT大鼠中观察到的相当。关于给药期，1.2% DEHP的一般毒性在整个实验期都很明显，10 ppm DEN的遗传毒性在给药2周后即可检测到，并在4周时进一步增加。这些结果表明，使用gpt delta大鼠的联合检测可以通过标准的4周给药方案检测一般毒性和遗传毒性。因此，这种使用gpt delta大鼠的检测方法将适用于风险评估，包括早期检测遗传毒性致癌物，并最终有助于降低人类因环境化学物质而患癌症的风险。
