A correlation of Salmonella mutagenicity with DNA adducts induced by the cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.
A correlation of Salmonella mutagenicity with DNA adducts induced by the cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.
复制标题
沙门氏菌致突变性与熟食诱变剂 2-氨基-1-甲基-6-苯基咪唑并[4,5-b]吡啶诱导的 DNA 加合物的相关性。
作者：
M. Malfatti;N. Shen;R. Wu;K. Turteltaub;J. Felton
在鼠伤寒沙门氏菌菌株TA 98（uvr B缺陷型）和TA 1978（uvr B有效型）中研究了杂环胺熟食诱变剂2-氨基-1-甲基-6-苯基咪唑[4，5-B]吡啶（PhIP）的细菌致突变性与DNA加合物的相关性。使用改良的艾姆斯/沙门氏菌微悬浮液测定法将细菌细胞暴露于PhIP。将从90分钟预孵育和洗涤产生的一半细胞铺板用于回复突变体形成，而剩余的一半通过32 P-后标记进行DNA加合物分析。在TA 98中，在5.5和17 μ M的PhIP浓度下，分别在10 x 10（-7）和21 x 10（-7）的RAL（相对加合物标记）下检测到DNA加合物。这分别对应于28.8和20.9加合物/回复突变体。这些值基于以下假设：75个DNA碱基区域内只有4个重复GC碱基是PhIP诱导突变的基因靶位点。在TA 1978中，在检测的任何PhIP浓度下均未检出高于背景的回复突变体。然而，在223和1116 μ M PhIP下，分别检测到每个核苷酸11 × 10 ~（-7）和21 × 10 ~（-7）的DNA加合物。缺乏可检测的回复突变体，但存在DNA加合物，表明在90 min预孵育期间确实发生了突变前病变。据推测，当在平板接种前去除S9活化系统和PhIP时（通过用磷酸盐缓冲盐水洗涤），含有完整uvrB修复系统的细胞在平板上孵育期间修复了病变。总之，通过加合物诱导回复突变体似乎相当有效，因为在切除修复缺陷型细菌中的一个突变事件需要约25个加合物。
The correlation of bacterial mutagenicity with DNA adducts from the heterocyclic amine cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated in Salmonella typhimurium strains TA98 (uvrB deficient) and TA1978 (uvrB proficient). Bacterial cells were exposed to PhIP using a modification of the Ames/Salmonella microsuspension assay. Half of the cells, generated from a 90 min pre-incubation and washing, were plated for revertant formation while the remaining half was subjected to DNA adduct analysis via 32P-postlabeling. In TA98, DNA adducts were detected at an RAL (relative adduct labeling) of 10 x 10(-7) and 21 x 10(-7) at PhIP concentrations of 5.5 and 17 microM, respectively. This corresponded to 28.8 and 20.9 adducts/revertant, respectively. These values were based on the assumption that only four repeating GC bases within a 75 DNA base region is the gene target site for PhIP induced mutations. In TA1978, no revertants above background were detected at any concentration of PhIP tested. DNA adducts, however, were detected at 11 x 10(-7) and 21 x 10(-7) adducts per nucleotide at 223 and 1116 microM PhIP, respectively. The lack of detectable revertants, but the presence of DNA adducts, suggests pre-mutational lesions did occur during the 90 min pre-incubation. Presumably, when the S9 activating system and PhIP were removed (via washing with phosphate buffered saline) prior to plating, the cells containing an intact uvrB repair system repaired the lesions during the incubation time on the plates. In conclusion, the induction of revertants by adducts appears quite efficient, as approximately 25 adducts are required for one mutational event in the excision repair deficient bacteria.