D'Ambrosio S M, Setlow R B
J Environ Pathol Toxicol. 1980 Aug;4(1):181-91.
As shown previously, newly synthesized DNA from Chinese hamster, excision proficient and excision deficient xeroderma pigmentosum (XP) cells treated with split doses of N-acetoxy-acetylaminofluorene (AAAF) or ultraviolet radiation (uv) is larger in size than DNA from cells treated with only the single dose. In this report we determined the effects of caffeine, an inhibitor of postreplication repair, upon enhancement of repair by a split dose treatment with AAAF. Caffeine was added to cells either immediately following the first or the second dose of AAAF and the size of newly synthesized DNA was determined by alkaline sucrose gradient sedimentation. Results showed that: (a) the DNA from V79 and XP cells incubated with caffeine between the first and second dose of AAAF was smaller in size than DNA from cells not incubated with caffeine; (b) caffeine exhibited a lesser effect when added after the second dose during the pulse-chase; and (c) caffeine has little effect upon daughter DNA of normal human cells treated with single or split doses of AAAF. These data indicate that caffeine interferes with the enhancement of postreplication repair in V79 and XP cells treated with AAAF.
如前所示，用分次剂量的N-乙酰氧基-乙酰氨基芴（AAAF）或紫外线（uv）处理的中国仓鼠、切除修复 proficient 和切除修复 deficient 的着色性干皮病（XP）细胞新合成的DNA，其大小比仅用单次剂量处理的细胞的DNA更大。在本报告中，我们确定了复制后修复抑制剂咖啡因对用AAAF分次剂量处理增强修复的影响。在第一次或第二次AAAF剂量后立即将咖啡因添加到细胞中，并通过碱性蔗糖梯度沉降法测定新合成DNA的大小。结果表明：（a）在第一次和第二次AAAF剂量之间用咖啡因孵育的V79和XP细胞的DNA，其大小比未用咖啡因孵育的细胞的DNA小；（b）在脉冲追踪期间第二次剂量后添加咖啡因时，其效果较小；（c）咖啡因对用单次或分次剂量的AAAF处理的正常人细胞的子代DNA几乎没有影响。这些数据表明，咖啡因会干扰用AAAF处理的V79和XP细胞中复制后修复的增强。
