γ线全身照射对大鼠肝癌细胞核RNA合成的影响及其机制的研究

作者观察了8Gy γ线全身照射正常和DEN诱发的肝癌大鼠其肝(癌)细胞核RNA合成的辐射生物效应,发现:<1>正常大鼠在受照射后4h出现一过性的RNA合成增高期,而后表现为抑制,出现双相效应;而肝癌大鼠在受照后4和18h均表现为強烈抑制;<2>在抑制了内源性染色质模板后,转录外源模板的游离型RNA聚合酶出现与染色质结合型酶相似的辐射效应,提示射线可直接影响RNA聚合酶;<3>在照射后4和18h,RNA聚合酶Ⅱ的活性变化率显著高于酶Ⅰ,提示酶Ⅱ及其复合体成分对射线更敏感;<4>肝癌大鼠在受照射后其核RNA合成的抑制与转录活性RNA聚合酶分子数目的减少以及酶的催化效率(延长速度)减低有关,而正常大鼠则是通过不同的机制实现。

Effect of Gamma-ray Whole-body Irradiation on RNA Synthe sis of Rat Hepatoma Nuclei in vitro and Studies of Its Mechanism

Normal and hepatoma-bearing rats, Induced by Dietnyinrtosamine(D(?)N), were exposed to 8 Gy ~(60)Co Gamma-ray. Template-engaged and free RNA polymerase activities in isolated rat liver and hepatoma nuclei,the relative numbers of transcribing active RNA polymerase molecules and elongation rates were observed at 4 and 18 hours after irradiation and comparision was made with corresponding non-irradiated control animals. The results showed that normal rats had a temporal increase and subsequent inhibition in liver RNA synthesis. Activities of total template-engaged RNA polymerase, polymerase Ⅰ and Ⅱ increased at 4 hours and decreased at 18 hours after exposure. Changes of free RNA polymerase were similar to that of engaged. This gave us an impression that irradiation could effect RNA polymerase directly. But the activities of RNA polymerase in both pools in hepatoma-bearing rats exhibited a strong inhibition at the two observed times after irradiation. Not only the relative numbers of transcribing active polymerase but also elongation rates in RNA chains decreased dramatically. No matter which cell nuclei, the activities of RNA polymerase Ⅱ showed a significantly greater alterations than polymerase Ⅰ,suggesting a stronger sensitivity for RNA polymerase Ⅱ transcribing complex to irradiation.