Norppa H, Hirvonen A, Järventaus H, Uusküla M, Tasa G, Ojajärvi A, Sorsa M
Finnish Institute of Occupational Health, Helsinki.
Carcinogenesis. 1995 Jun;16(6):1261-4. doi: 10.1093/carcin/16.6.1261.
The individual genotoxic response of cultured human lymphocytes to diepoxybutane (DEB), an epoxide metabolite of 1,3-butadiene, shows a bimodal distribution. Blood donors can be classified as either DEB-sensitive or DEB-resistant on the basis of the frequency of sister chromatid exchanges (SCEs) induced by DEB in whole-blood lymphocyte cultures. The genetic basis of this phenomenon has thusfar been unknown. To investigate if differences in the ability of individuals to detoxify DEB could explain the bimodal response, sister chromatid exchanges (SCEs) induced by a 48-h treatment with DEB (2 and 5 microM) were analyzed in whole-blood lymphocyte cultures of 20 human donors with known genotypes of two polymorphic glutathione S-transferases (GSTs), GSTT1 and GSTM1. Both polymorphisms include a homozygous null genotype lacking the respective GST gene and isozyme. The mean frequency of SCEs/cell was 1.6 times higher among GSTT1 null donors (n = 8) than GSTT1 positive donors (n = 12) at both 2 microM DEB (mean 67.3 versus 40.9) and 5 microM DEB (mean 123.2 versus 77.5), with no overlapping in DEB-induced individual SCE frequencies between the two genotypes. Thus, all DEB-sensitive individuals were of the GSTT1 null genotype, while all DEB-resistant persons had a detectable GSTT1 gene. A significant (P < 0.05) negative correlation (r = -0.65 at 5 microM, r = -0.56 at 2 microM) was obtained in the GSTT1 positive donors between DEB-induced individual SCE frequency and RBC GSTT1 activity, measured by formaldehyde formation from dichloromethane; the GSTT1 null individuals showed no GSTT1 activity. At 5 microM DEB, the lymphocyte cultures of the GSTT1 null donors also had a significantly decreased replication index, indicating an impact of GSTT1 genotype on the cytotoxicity of DEB. No influence on DEB-induced SCEs or cytotoxic effects was observed for GSTM1 genotype. It is concluded that sensitivity to in vitro SCE induction by DEB is explained by the lack of GSTT1.
培养的人淋巴细胞对1,3 - 丁二烯的环氧化代谢物1,2 - 二环氧丁烷（DEB）的个体遗传毒性反应呈双峰分布。根据全血淋巴细胞培养中DEB诱导的姐妹染色单体交换（SCE）频率，献血者可分为DEB敏感型或DEB抗性型。迄今为止，这种现象的遗传基础尚不清楚。为了研究个体对DEB解毒能力的差异是否可以解释双峰反应，在20名已知两种多态性谷胱甘肽S - 转移酶（GST）GSTT1和GSTM1基因型的人类献血者的全血淋巴细胞培养物中，分析了用DEB（2和5 microM）处理48小时诱导的姐妹染色单体交换（SCE）。这两种多态性都包括缺乏相应GST基因和同工酶的纯合无效基因型。在2 microM DEB（平均67.3对40.9）和5 microM DEB（平均123.2对77.5）时，GSTT1无效供体（n = 8）中SCEs/细胞的平均频率比GSTT1阳性供体（n = 12）高1.6倍，两种基因型之间DEB诱导的个体SCE频率没有重叠。因此，所有DEB敏感个体均为GSTT1无效基因型，而所有DEB抗性个体都有可检测到的GSTT1基因。在GSTT1阳性供体中，通过二氯甲烷形成甲醛测定的DEB诱导的个体SCE频率与红细胞GSTT1活性之间存在显著（P < 0.05）负相关（5 microM时r = -0.65，2 microM时r = -0.56）；GSTT1无效个体未显示GSTT1活性。在5 microM DEB时，GSTT1无效供体的淋巴细胞培养物的复制指数也显著降低，表明GSTT1基因型对DEB的细胞毒性有影响。未观察到GSTM1基因型对DEB诱导的SCE或细胞毒性作用有影响。结论是，对DEB体外诱导SCE的敏感性可由GSTT1的缺乏来解释。
