Mirsalis J C, Tyson C K, Butterworth B E
Environ Mutagen. 1982;4(5):553-62. doi: 10.1002/em.2860040506.
The in vivo-in vitro hepatocyte DNA repair assay has been shown to be useful in the evaluation of the carcinogenic potential of chemicals. The purpose of this study was to apply this assay to determining the genotoxicity of the compounds from a wide variety of structural classes. Male Fischer-334 rats were treated by gavage or ip injection with compounds dissolved in either corn oil, water, or dimethyl sulfoxide (DMSO). At selected times after treatment, hepatocytes were isolated by liver perfusion and cultured with 3H-thymidine, Unscheduled DNA synthesis (UDS) was measured by quantitative autoradiography as net grains/nucleus (NG); greater than or equal to 5 NG was considered positive. Water, corn oil, or DMSO controls produced -3 to -6 NG with less than or equal to 6% of the cells in repair. All genotoxic hepatocarcinogens tested produced strong positive responses of greater than 15 NG including dimethylnitrosamine, 2-acetylaminofluorene (2-AAF), azoxymethane, 1,2-dimethylhydrazine, benzidine, aflatoxin B1, 2,6-dinitrotoluene, and 2,4-diaminotoluene. The noncarcinogen, 2,6-diaminotoluene, was negative. The mutagen and rat brain carcinogen methyl methanesulfonate (MMS) and the rat pancreatic carcinogen azaserine were also positive. The carcinogens benzo(a)pyrene and 7,12-dimethylbenz(a)anthracene yielded from -2 to -4 NG. This negative response is consistent with their lack of carcinogenic activity in rat liver. MMS produced the greatest amount of UDS 2 hr after treatment whereas 2-AAF did not induce its maximum response until 12 hr post-treatment. The potent hepatotoxin carbon tetrachloride induced a 40-fold elevation in DNA replication 48 hr after a 400 mg/kg dose, but no UDS was observed at 2, 12, 24, or 48 hr post-treatment. The weak hepatocarcinogen safrole induced no UDS suggesting that it is either nongenotoxic or is metabolized to an active form at an extremely slow rate following a single administration. These results demonstrate that this assay is valuable for the detection and study of a variety of genotoxic carcinogens.
体内-体外肝细胞DNA修复试验已被证明在评估化学物质的致癌潜力方面很有用。本研究的目的是应用该试验来确定来自各种结构类别的化合物的遗传毒性。将雄性Fischer-334大鼠通过灌胃或腹腔注射给予溶解于玉米油、水或二甲基亚砜（DMSO）中的化合物。在处理后的选定时间，通过肝脏灌注分离肝细胞并用3H-胸腺嘧啶培养，通过定量放射自显影测量非预定DNA合成（UDS），以净颗粒数/细胞核（NG）表示；大于或等于5 NG被认为是阳性。水、玉米油或DMSO对照组产生-3至-6 NG，修复细胞比例小于或等于6%。所有测试的遗传毒性肝癌致癌物均产生大于15 NG的强阳性反应，包括二甲基亚硝胺、2-乙酰氨基芴（2-AAF）、偶氮甲烷、1,2-二甲基肼、联苯胺、黄曲霉毒素B1、2,6-二硝基甲苯和2,4-二氨基甲苯。非致癌物2,6-二氨基甲苯为阴性。诱变剂和大鼠脑致癌物甲磺酸甲酯（MMS）以及大鼠胰腺癌致癌物偶氮丝氨酸也呈阳性。致癌物苯并(a)芘和7,12-二甲基苯并(a)蒽产生-2至-4 NG。这种阴性反应与其在大鼠肝脏中缺乏致癌活性一致。MMS在处理后2小时产生的UDS量最大，而2-AAF直到处理后12小时才诱导出最大反应。在400 mg/kg剂量的四氯化碳处理48小时后，强力肝毒素诱导DNA复制升高40倍，但在处理后2、12、24或48小时未观察到UDS。弱肝癌致癌物黄樟素未诱导UDS，表明它要么无遗传毒性，要么在单次给药后以极慢的速率代谢为活性形式。这些结果表明该试验对于检测和研究各种遗传毒性致癌物具有重要价值。
