低剂量氚水对发育中鼠中枢神经系统的影响及其机理研究

Effects of lowdose tritiated water on the developing central nerve system and their mechanisms

目的研究低剂量氚水对发育中鼠的中枢神经系统的影响，为评价核电站排放氚的危险度及制定核安全防护标准提供实验基础资料。方法孕龄１２５天和１３０天的Ｃ５７ＢＬ／６Ｊ小鼠及Ｗｉｓｔａｒ大鼠，单次腹腔注射氚水活度分别为２４０９、４８１８和１４４５４×１０４Ｂｑ／ｇ体重。检测仔代鼠神经行为、学习能力及记忆功能的改变。采用膜片钳技术观察脑海马神经元Ｃａ２＋电流幅度的变化。利用形态学和ＤＮＡ电泳分析的生物化学方法对培养的脑细胞进行凋亡的鉴定、用ＳＤＳＰＡＧＥ和ＷｅｓｔｅｒｎＢｌｏｔｉｎｇ方法检测培养的脑细胞Ｐ５３蛋白的变化。结果鼠出生前经氚照射可导致出生后神经行为早期的兴奋状态转为后期的抑制状态；学习能力及记忆功能明显下降；发育中的神经元表现出Ｃａ２＋电流降低、凋亡增加、ＤＮＡ梯状图谱以及Ｐ５３蛋白表达增高，在培养第４天，３Ｈ氚化胸腺嘧啶组和氚水组细胞凋亡百分比分别为２４５％和２８１％，而对照组则为８１％～９３％。结论导致氚辐射对鼠中枢神经系统损伤的物质基础与氚照射导致脑海马神经元Ｃａ２＋电流幅度下降、脑细胞凋亡增加及Ｐ５３蛋白表达异常等因素有密切关系。

Objectives To provide experimental data for evaluating tritium risk of nuclearenergy plant and instituting safety protection standard of nuclear effects of lowdose tritiated water(HTO) on the developing central nerve system. Methods Pregnant adult C57BL/6J strain mice and Wistar rats were irradiated with betarays from HTO by a single intraperitoneal injection on the 125 th and 13 th day of gestation The activity of HTO was(104 Bq/gBW) 2409,4818 and 14454, respectively Neurobehavior and learning and memory ability were tested. Ca2+ currents of hippocampal neurons were examined by patchclamp. Apoptosis of brain cells was detected morphologically and biochemically by DNA electrophoresis. SDSPAGE and Western blotting were used to detect P53 protein in the cultures Results After irradiation with betarays from HTO in utero, the offspring showed hyperactivity in their young age period and then showed depressionhypoactivity in adulthood. The exposed animals had difficulties in both learning and memory retention and the developing neurons of the central nerve system showed lower Ca2+ currents, higher number of apoptosis, a typical ladder pattern DNA and increasing P53 protein Conclusions Lower Ca2+ currents, higher number of apoptosis of brain cells and abnormal expression of P53 protein were the substance basis of the damage of central nerve system caused by tritium