2017 年 82 巻 2 号 p. 183-191
The effects on genotoxicity of AgNO3 (10 µM, 20 µM and 50 µM) in Allium cepa L. were studied under 6 h of treatment followed by recovery experiments. The oxidative damage caused by AgNO3 reduced the root length, catalase (CAT) activity and mitotic index. Enhanced antioxidant enzyme activities were noticed in ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) activity to scavenge the oxidative stress. The effect of toxicity was found to be dose dependent in antioxidative enzyme level and more pronounced in root systems than shoot. Evan’s blue uptake was more in the treated root cells over control as a cell death parameter that indicates cytotoxicity. Recovery experiments of 48 h showed significant changes of antioxidative enzymes towards normalization of cell. AgNO3 treated tissues produced H2O2 and O2− that damaged the somatic chromosomes, leading to formation of spindle abnormalities (multipolarity, sticky bridge in anaphase, early separation, clumping of chromosomes, late separation, laggard chromosome) and direct chromosomal damage, i.e., chromosome break and chromosome erosion. Recovery experiments revealed reduction of abnormalities from ca. 48% of the dividing cell to ca. 3.5% in metaphase and ca. 36.5% to ca. 5.5% in anaphase cells that was near to control. Our results indicate that short exposure of low doses of Ag-induced oxidative damage can be reversible in antioxidant enzyme and chromosomal level by repairing the cell damage. This experiment elucidates the role of reactive oxygen intermediates in silver (Ag)-induced DNA damage, cell death and oxidative cell damage.
