Andersson H C, Kihlman B A
Department of Genetics, University of Uppsala, Sweden.
Mutat Res. 1987 Nov;181(1):173-85. doi: 10.1016/0027-5107(87)90297-1.
The frequencies of chromatid aberrations produced in roots of Vicia faba by clastogenic (chromosome-damaging) agents were strongly enhanced by exposing the root-tip cells to inhibitors of DNA synthesis during the G2 phase. Chromosome damage produced by both S-dependent (maleic hydrazide, methyl methanesulfonate, thio-TEPA) and S-independent (X-rays, streptonigrin) mechanisms was enhanced by the inhibitor treatments. The types of aberrations affected by the inhibitors were mainly chromatid gaps and breaks and isochromatid breaks of the non-union type. Most effective among the inhibitors tested were hydroxyurea (HU) and 5-fluorodeoxyuridine (FdUrd). Post-treatments with caffeine were effective in enhancing clastogen-induced chromosome damage when given during the S phase. All types of aberrations, exchanges as well as breaks, were enhanced by the post-treatments. When given during the G2 phase, caffeine enhanced only the frequency of chromatid aberrations produced by X-rays. The enhancement was slight and obtained only when the cells were irradiated in the G2 phase and immediately post-treated with caffeine. Clastogen-treated cultures of human lymphocytes responded to post-treatments with inhibitors of DNA synthesis in very much the same way as clastogen-treated root-tip cells of Vicia faba. Thus, the frequencies of chromatid gaps and breaks and isochromatid breaks of the non-union type were strongly enhanced by exposing clastogen-treated lymphocytes to inhibitors of DNA synthesis during the G2 phase. The efficiency of the inhibitors, however, varied considerably in the two materials. On the whole, the number of inhibitors capable of enhancing induced chromosome damage was much larger in lymphocytes than in bean root tips. Only HU was equally effective in both materials. The most striking difference between the two materials was found when caffeine was given as a post-treatment. Thus, in human lymphocytes the frequencies of chromatid aberrations induced by most clastogenic agents were strongly enhanced when caffeine was given during the G2 phase, but little affected by post-treatments with caffeine during the S phase.
通过在G2期将蚕豆根尖细胞暴露于DNA合成抑制剂，致断裂剂（染色体损伤剂）在蚕豆根中产生的染色单体畸变频率显著增加。依赖于S期（马来酰肼、甲基磺酸甲酯、硫代磷酸三乙酯）和不依赖于S期（X射线、链黑菌素）机制产生的染色体损伤都因抑制剂处理而增加。受抑制剂影响的畸变类型主要是染色单体间隙和断裂以及非联合型等染色单体断裂。在所测试的抑制剂中，羟基脲（HU）和5-氟脱氧尿苷（FdUrd）最有效。在S期给予咖啡因后处理可有效增强致断裂剂诱导的染色体损伤。所有类型的畸变，包括交换和断裂，都因后处理而增加。在G2期给予咖啡因时，仅增强了X射线产生的染色单体畸变频率。这种增强很轻微，只有当细胞在G2期受到照射并立即用咖啡因进行后处理时才会出现。用致断裂剂处理的人类淋巴细胞培养物对DNA合成抑制剂后处理的反应与用致断裂剂处理的蚕豆根尖细胞非常相似。因此，通过在G2期将用致断裂剂处理的淋巴细胞暴露于DNA合成抑制剂，非联合型染色单体间隙和断裂以及等染色单体断裂的频率显著增加。然而，抑制剂在这两种材料中的效率差异很大。总体而言，能够增强诱导染色体损伤的抑制剂数量在淋巴细胞中比在蚕豆根尖中多得多。只有HU在两种材料中同样有效。当给予咖啡因作为后处理时，发现这两种材料之间最显著的差异。因此，在人类淋巴细胞中，当在G2期给予咖啡因时，大多数致断裂剂诱导的染色单体畸变频率显著增加，但在S期用咖啡因后处理影响很小。
