Research and development of transgenic mouse for biological effect assesment of tritium

我们将转基因小鼠应用于氚-贝塔射线诱发突变的分析。在目前的研究中。用Gossen培育的Ingeno小鼠通过电离辐射检测缺失突变。虽然传统的转基因小鼠不适合研究辐射诱发突变，但Ingeno小鼠通过用pUR228载体转染40个拷贝的LacZ基因有望用于辐射诱导突变的研究。然而，要想实际应用，还有几个问题需要克服。其中，我们成功地改进了突变LacZ基因在大肠杆菌中的修复方法以及p-Gal对突变基因的阳性选择等技术问题，为氚生物学研究奠定了基础。用Ingeno小鼠测定的中子束和碳束的RBE与前人报道的一致，证实了这一点。这些结果还表明，氚的相对生物效应约为2。然而，Ingeno小鼠的辐射敏感性较低，即突变频率分别为0.5Gy和10Gy时的3.22*10^&lt；-4&gt；，5.37*10^&lt；-4&gt；，4.68*10^&lt；-4&gt；，显示出进一步提高辐射敏感性的必要性。利用含有单个人X染色体的仓鼠杂交细胞，阐明了Ingeno小鼠灵敏度较低的原因，表明有可能开发出对辐射敏感的新型转基因小鼠，其灵敏度是常规检测的100倍。因此，我们的结果表明转基因小鼠在未来的氚生物学研究中是有用的，例如对DNA损伤或对氚的刺激反应的特异性。

We applied the transgenic mouse for analysis of tritium beta rays-induced mutation. In prsent study. Ingeno mouse developped by Gossen was used to detect the deleted mutation by ionizing radiation. Although coventional transgenic mouse is not appropriate for study of radiation-induced mutation, Ingeno mouse is expected to be useful for such mutations by transfection of 40 copy LacZ gene with plasmid pUR228. However, there are several problems to overcome for practical utilization. Among them, we successfully improved here technical problems, such us rescure methods of mutated lacZ gene into E.Coli and also positive selection of mutated gene by p-gal, indicating the availability for tritium biological study. This is confirmed by the evidences that RBE of neutron and carbon beam assayd by using Ingeno mouse is in agreement with that reported previously by others. These results also suggest that RBE of tritium is approximately 2. However, Ingeno mouse was appeared to be less radiation sensitive, i.e., 3.22*10^<-4>,5.37*10^<-4>,4.68*10^<-4> of mutation freguency at 0.5Gy, 10Gy of irradiation dose, respectively, and show necessity of further improvement as to radiation sensitivity. Using the hamster hybrid cells containing a single human X chromosome, we clarified the reason for less sensitivity of Ingeno mouse, suggesting the possibility of develop for radiation sensitive new transgenic mouse, which is 100-fold more sensitive than conventional assay. Consequently, our results demonstrated the usefulness of trasgenic mouse for future tritium biological study, such as specificity of DNA damage or hormesis response by tritium.