Studies of biological effects of fluoride stannous and UV short in Escherichia coli BH110

Full text: The amount of UV rays on the Earth's surface has increased due to depletion of the ozone layer, and this has worried society, since these radiation although not considered ionizing can cause damage to biological membrane and especially to DNA. The DNA has cell repair mechanisms that can work in lesions caused by electromagnetic radiation such as ultraviolet -short (UV C)and agents causing oxidative stress, such as tin salts. Among the repair mechanisms can highlight the adaptive repair, which consists of smaller doses to cells pre-exposure of an oxidizing agent, and when these cells are exposed to larger doses of the agent even if there is a reduction in mortality rate which leads to complete that repair mechanisms are activated in the pre-exposure reducing cell mortality. Several publications have shown the genotoxic effects of stannous salts such as stannous fluoride (SnF₂), which shows the importance of the study, since these salts are widely used in industry as components in toothpastes and mouthwashes. So we check whether pretreatment with UV C is able to induce adaptive response reducing the cytotoxic effects caused by exposure of the strains to SnF₂. We use a strain of Escherichia coli BH110 (BH110 E. coli) deficient in three genes (fpg, nfo and xth) involved in the excision repair bases. To verify the induction of adaptive response to strain BH110 was exposed to various doses of UV C and then treated with SnF₂ a concentration of 110 u M. Our results showed that the LD10 of strain BH110 is 20 J/m² and pre-treatment with UV C does not seem to induce adaptive repair in BH110 strains. (Author)