活体内姐妹染色单体交换的研究

Study on sister chromatid exchange in vivo

姐妹染色单体互换(sister chromatid exchange,SCE),近年来已广泛用于各种诱变剂和致癌剂的检测。这一方法对于染色体的分子结构,DNA的复制、损伤、修复和细胞周期等生物学的基本问题也提供了很多有价值的信息。以往对于SCE的研究大多在离体条件下进行,这虽简单易行,但和体内相比仍有其局限性。特别是作为诱变因子的检测手段,体内实验和体外实验的结果往往不一致,而体内实验更能令人信服,因为体外条件下无体内活化和解毒系统,已经发现相当一部份的强化因子在离体条件下诱变活力很强,而在活体内则大大减弱甚或无诱变作用。当然也有些诱变因子在体外不引起SCE的增加,而在活体内经过活化以后,毒性加大,致使SCE频率增高。

The effects of different dosage of 5′-bromodeoxyuridine(BrdU) on the frequencies of SCE of the bone marrow cells of Chinese hamsters(CH) in vivo were studied by a single intratoneal injection of activated charcoal-suspended BrdU into hamsters with an average weight of about 23g.The results indicated that there was no significant difference among SCEs induced by the dosage of 5mg/body,10mg/body,and 15mg/body,and thereby 3 per cell for the “spontaneous”frequency of SCEs should be concluded. The frequencies of SCE highly increased at the dosage of above 20mg/body, while at the dosage of 80mg/body, the frequency of SCE induced was nearly 2.80 times as high as that of 5mg/body.In accordance with our results, a new concept was suggested that there must have been a threshold of BrdU dosage in approximation of the frequency of“spontaneous”SCE in mammals,and that of the SCEs would significantly increase if the dosages of BrdU were larger than the threshold.The frequencies of SCE induced by cyclopho-sphamidum(CP),actinomycin D(AD).Caffeine(Caf),nitrogen-mustard(NM) and fluoro-uracilum (FU) show that all of the drugs tested markedly increase SCEs,among them,NM has the most significant effect and Caf,FU the weakest.