氚照射生物效应的实验研究

A review of experimental studies on biological effects of tritium exposure

目的 综合概括了过去十几年所作的氚照射生物效应系统研究的实验结果。 方法该研究着重于低剂量氚照射对健康造成可能影响的实验研究 ,研究了氚在妊娠和哺乳动物体内的分布、代谢和剂量估算 ;遗传学效应 (初级卵母细胞存活率、精原细胞存活率、卵母细胞或精母细胞的显性致死突变、精原细胞显性骨骼突变。通过C 分带Giemsa染色 ,分析了精母细胞中期 1的染色体畸变 ) ;致畸效应 (生长发育、神经行为、脑细胞学和脑神经递质 ) ,同时也研究了离体氚水和有机结合氚对脑细胞增殖、分化、Ca2 +电流、细胞周期、p5 3表达以及细胞凋亡的诱导等。 结果 选用多项生物终点进行了氚 β射线与γ射线或X射线的比较研究 ,估算了氚 β射线遗传危险度〔以精原细胞的显性骨骼突变作为生物终点 ,氚 β射线剂量为 0 19、0 3 8、0 66和 1 0 1Gy时 ,突变率 (×10 4/ 10 6 Gy)分别为 2 72 98、0 80 62、0 684 3和 1 3 0 4 2〕、相对生物效能 (分别以整体研究的遗传和生殖、以离体研究的细胞增殖和分化参数作为生物终点并获得的氚 β射线RBE值变化在 2 2 4到2 99,4 6到 8 7范围内 )以及致畸阈值 (以大鼠和小鼠为实验对象观察的 5 6项生物学指标中氚致畸阈剂量约 80 %指标分布在 0 0 3～ 0 0 9cGy范围内 ,约 2 0 %?

Objective\ This review briefly describes the basic experimental results of a systemic study on radiobiological effects of tritium,which was carried out by the Group of Tritium Study at Laboratory of Industrial Hygiene for over 10 years.\ Methods The study focused on the possible health effects from low dose level tritium exposure and investigations covered many aspects including distribution,metabolism,dosimetry,genetic damage(primary oocyte survival and spermatogonia survival rates,dominant lethal mutations of oocytes or spermatocytes, and dominant skeleton mutations of spermatocytes,chromosomal aberrations analyzed by C banding of spermatocytes at metaphase Ⅰ),teratogenic effect (postnatal development,neurobehavoiral changes,cellular changes of brain and neuropeptide) after exposure to tritiated water (HTO) in vivo, and effects of tritium exposure from HTO or organically bound tritiated compounds (OBT) on cellular proliferation and differentiation,Ca 2+ conductance,cell cycle,p53 expression,and apoptosis induction in neurons in vitro. Results Many biological endpoints were used to estimate the genetic risk (when using dominant skeleton mutations of spermatocytes as the biological endpoint,the mutation rates (×10 4 /10 6 Gy) of 0.19,0 38,0 66 and 1.01 Gy groups were 2.7298,0.8062,0.6843 and 1.3042,respectively),relative biological effectiveness (a variety of RBE values for tritium were obtained ranging from 2.24 to 2.99 and from 4.6 to 8.7 by using in vivo genetic and reproductive effects,and in vitro cellular proliferation and differentiation parameters as the biological endpoints,respectively),and teratogenetic threshold (in about 80% of the observed 56 parameters in rats and mice indicating that the threshold dose for prenatal HTO exposure ranged from 0.03 Gy to 0.092 Gy,and from 0.093 to 0.30 Gy for the other 20% parameters). Conclusion The damage induced by low dose tritium cannot be ignored.\;