Sofuni T, Honma M, Hayashi M, Shimada H, Tanaka N, Wakuri S, Awogi T, Yamamoto K I, Nishi Y, Nakadate M
National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158, Japan.
Mutagenesis. 1996 Jul;11(4):349-55. doi: 10.1093/mutage/11.4.349.
Under the auspices of the Ministry of Health and Welfare of Japan and the Japanese Pharmaceutical Manufacturer Association, a collaborative study of the mouse lymphoma assay (MLA) was conducted by 42 Japanese laboratories and seven overseas laboratories to clarify the performance of the MLA for the detection of in vitro clastogens and spindle poisons. Twenty-one chemicals that were positive in in vitro chromosomal aberration assays (CA) but negative in bacterial reverse mutation assays (BRM) were examined by the MLA using the microwell method. All chemicals were coded, and each chemical was tested by two or three laboratories. Positive responses were obtained with 14 chemicals: mitomycin C (an internal positive control), arsenic trioxide, cadmium sulphate, chlorendic acid, cytosine arabinoside, diethylstilbestrol, eugenol, 5-fluorouracil, griseofulvin, hexamethyl phosphoramide, hydroxyurea, methotrexate, monocrotaline and pentachloroethane. Two chemicals (benzene and chlorodibromomethane) showed positive responses in one of two laboratories and were judged probably positive chemicals. Three chemicals (bromodichloromethane, isophorone and tetrachloroethane) were inconclusive because of a marginal response in one laboratory and a negative response in the other. Urethane was judged probably negative because two laboratories out of three showed clear negative responses. Dideoxycytidine (DDC) was a clear negative chemical in this study. The present results showed that 75.0% of the test chemicals (15/20, excluding mitomycin C) were positive, 15.0% (3/20) were inconclusive, and 10.0% (2/20) were negative. This suggests that the MLA may detect a majority of CA-positive chemicals. The inconclusive chemicals, however, are critical for the judgement of the MLA potential to detect clastogens. The findings that DDC was clearly negative suggests that the MLA may not be able to detect some clastogens. To clarify these issues, we began the second phase of the collaborative study with other BRM-negative and CA-positive chemicals.
在日本厚生劳动省和日本制药商协会的支持下，42家日本实验室和7家海外实验室对小鼠淋巴瘤试验（MLA）进行了一项合作研究，以阐明MLA在检测体外致断裂剂和纺锤体毒物方面的性能。使用微孔法，对21种在体外染色体畸变试验（CA）中呈阳性但在细菌回复突变试验（BRM）中呈阴性的化学物质进行了MLA检测。所有化学物质均进行了编码，每种化学物质由两到三个实验室进行检测。14种化学物质获得了阳性反应：丝裂霉素C（内部阳性对照）、三氧化二砷、硫酸镉、氯菌酸、阿糖胞苷、己烯雌酚、丁香酚、5-氟尿嘧啶、灰黄霉素、六甲基磷酰胺、羟基脲、甲氨蝶呤、野百合碱和五氯乙烷。两种化学物质（苯和二溴一氯甲烷）在两个实验室中的一个显示出阳性反应，被判定可能为阳性化学物质。三种化学物质（二氯一溴甲烷、异佛尔酮和四氯乙烷）由于在一个实验室中反应微弱而在另一个实验室中呈阴性反应，结果不明确。氨基甲酸乙酯被判定可能为阴性，因为三个实验室中有两个显示出明显的阴性反应。双脱氧胞苷（DDC）在本研究中是明确的阴性化学物质。目前的结果表明，75.0%的受试化学物质（15/20，不包括丝裂霉素C）呈阳性，15.0%（3/20）结果不明确，10.0%（2/20）呈阴性。这表明MLA可能检测到大多数CA阳性化学物质。然而，结果不明确的化学物质对于判断MLA检测致断裂剂的潜力至关重要。DDC明显呈阴性的结果表明，MLA可能无法检测到某些致断裂剂。为了阐明这些问题，我们开始了与其他BRM阴性和CA阳性化学物质的合作研究的第二阶段。
