5例放射事故病人照后5.5年外周血淋巴细胞 HPRT 基因突变频率和突变谱的测定

Determination of the HPRT gene mutation frequency and mutation spectrum in the peripheral lymphocytes in 5 patients at 5.5 years after γ ray over exposure

通过克隆外周血淋巴细胞并用６巯基鸟嘌呤筛选次黄嘌呤磷酸核糖转移酶基因（ｈｙｐｏｘａｎｔｈｉｎｅｐｈｏｓｐｈｏｒｉｂｏｓｙｌｔｒａｎｓｆｅｒａｓｅ，ＨＰＲＴ）缺陷的突变细胞，测定了５例急性放射病人在受２．０～５．２Ｇｙ６０Ｃｏγ射线意外照射后５．５年外周血淋巴细胞ＨＰＲＴ基因突变频率。观察到细胞克隆效率、突变细胞克隆数、ＨＰＲＴ突变频率与受照剂量有一定的依赖性。用多引物聚合酶链反应（ＰＣＲ）扩增突变细胞ＨＰＲＴ基因全部９个外显子伴以琼脂糖凝胶电泳以分析基因突变谱。结果表明，高剂量受照病人的外显子缺失总数较低剂量者高。与照后３．５年和４．５年的突变谱比较，外显子缺失突变比例逐年下降，而点突变比例逐年升高。可能反映病人机体的恢复和受损ＤＮＡ的修复。

The mutation frequencies and mutation spectrum of hypoxanthine phosphoribosyltransferase (HPRT) gene were determined in the peripheral lymphocytes in 5 patients at 5.5 years after accidental over exposure to 2.0-5.2 Gy γ ray. By cloning of the lymphocytes and screening of the 6 thioguanine resistant mutant clones, the clonal efficiency, number of mutant clones,and HPRT gene mutation frequency were found to be related to the radiation dose. Multiplex polymerase chain reaction followed by agarose gel electrophoresis was used to detect the mutation in 9 exons of whole HPRT gene. The results showed that the total number of exon deletion in the patient receiving higher irradiation dose was higher than that in patient receiving lower dose. In comparison with the HPRT gene mutation spectra at 3.5 and 4.5 years after exposure, as the time elapsed, the percentage of exon deletion decreased stepwisely year by year, while the percentage of point mutation was elevated accordingly. This might reflect the gradual recovery of the patient and gradual repair of damaged DNA.