中文摘要：

目的：探讨ATM对电离辐射照射的毛细血管扩张共济失调症（ataxia telangiectasia，AT）患者皮肤的成纤维细胞系AT细胞（AT5BIVA）端粒酶活性的影响。方法：以源于正常人皮肤的成纤维细胞系GM细胞（GM0639）为对照，应用基于PCR的端粒重复扩增技术（telomeric repeat amplification protocal，TRAP）与高效液相色谱（HPLC）技术，定量分析细胞分别经0、1、3、5Gy ^60Coγ射线照射后以及经3 Gy ^60Coγ射线照射后继续培养2、24、48、72h，AT、空载体AT、ATM^＋-AT和GM细胞的端粒酶活性的变化。结果：未照射时，除GM细胞外，AT、空载体AT、ATM^＋-AT细胞均呈现较高的端粒酶活性表达，但ATM^＋-AT细胞的端粒酶活性明显低于AT和空载体AT细胞的端粒酶活性（P〈0．01），而后二者无明显差异（P〉0.05）；电离辐射照射后，AT、空载体AT、ATM^＋-AT和GM细胞的端粒酶活性均呈剂量依赖性和时间依赖性增强，且在相同剂量点与时间点，ATM^＋-AT细胞的端粒酶活性高于GM细胞（P〈0．01）（除5 Gy计量点外），但低于AT和空载体AT细胞（P〈0.01），而后二者无明显差异（P〉0.05）。结论：电离辐射可诱导细胞端粒酶活性表达；并且细胞端粒酶活性水平随剂量与时间的增加而增加；ATM可下调AT细胞端粒酶活性水平。推测端粒酶参与电离辐射诱导DNA损伤的修复。

英文摘要：

Objective：To investigate the effect of ataxia telangiectasia mutated （ATM） genes on telomerase activity of fibroblast cell line （ATSBIVA cells） from the skin of patients with ataxia-telangiectasia （AT） induced by ionizing radiation. Methods： Fibroblast cell line GM0639 originated from the skin of normal people was used as control. Cells were exposed to ^60Coγ irradiation at 0, 1, 3 and 5 Gy. The cells exposed to 3 Gy of ^60Coγ-rays were re-cultured for 2, 24, 48 and 72 h, respectively. PCR based telomeric repeat amplification protocol （TRAP） and HPLC methods were used to determine the telomerase activity in AT, ATM＋AT and GM0639 cells, respectively. Results：Except for GM0639 cells, AT, PEBS7- AT ATM＋AT cells showed high telomerase activity before ionizing radiation. But the ielomerase activity in ATM＋AT cells was significantly lower than that of AT and PEBS7-AT cells （P〈0.01）. The difference in telomerase activity between AT and PEBS7-AT cells was not significant （P〉0.05）. After exposure to ionizing radiation the telomerase activity in AT, PEBS7-AT, ATM ＋AT, and GM0639 cells were significantly increased in a dose- and time-dependent manners. At the same dose point and time point, the telomerase activity in ATM ＋AT cells were significantly higher than that of GM0639 cells （except 5 Gy point）, but still lower than that of AT and PEBS7 AT cells （P〈 0. 01）. But the telomerase activity in AT cells were not significantly different from that in PEBS7-AT cells （P）0.05）. Conclusion： Ionizing radiation induces the increase in telomerase activity in a dose- and time-dependent manners. ATM can down-regulate telomerase activity of AT cells before and after ionizing radiation. It indicates that telomerase participates in the repair process of DNA injury induced by ionizing radiation.