| Summary: | Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico === A radiaÃÃo ionizante à considerada um fator de risco para o desenvolvimento de diversos tipos de neoplasias pelos danos causados à molÃcula de DNA, sendo de extrema importÃncia, portanto, o monitoramento de populaÃÃes humanas expostas a ela. O municÃpio de Monte Alegre no estado do Parà apresenta uma das maiores Ãreas de mineraÃÃo do urÃnio do mundo, que se estende aos municÃpios vizinhos de Prainha e Alenquer. Este trabalho teve como objetivos a avaliaÃÃo do potencial genotÃxico do urÃnio presente em rochas nas residÃncias de indivÃduos dos municÃpios de Monte Alegre, Prainha e Alenquer atravÃs do ensaio do cometa alcalino em linfÃcitos perifÃricos e a determinaÃÃo das freqÃÃncias de polimorfismos nos genes de reparo do DNA XRCC1 e XRCC3 e no gene de metabolizaÃÃo GSTM1 atravÃs de seqÃenciamento direto de DNA. Na anÃlise do cometa alcalino, nÃo houve diferenÃa estatisticamente significante entre os Ãndices de Dano (IDs) das populaÃÃes de Monte Alegre (ID = 32,01  1,57), Prainha (ID = 45,80  1,12) e Alenquer (ID = 44,30  0,62) e o do controle negativo (ID = 42,00  5,75) (p > 0,05). AtravÃs do seqÃenciamento direto de DNA, observou-se a presenÃa de polimorfismos nos genes XRCC1 e XRCC3 em regiÃes de Ãntrons e de Ãxons. No gene XRCC1, as freqÃÃncias alÃlicas variantes para o polimorfismo Arg194Trp nas populaÃÃes de Monte Alegre, Prainha e Alenquer foram 12%, 13% e 7% e, para Arg399Gln, 28%, 30% e 32%, respectivamente. No gene XRCC3, as freqÃÃncias do alelo variante do polimorfismo Thr241Met encontradas nas populaÃÃes de Monte Alegre, Prainha e Alenquer foram, respectivamente, 28%, 13% e 33%. Em relaÃÃo ao gene GSTM1, as freqÃÃncias obtidas de ausÃncia do gene apresentaram os valores de 36%, 31% e 40%, respectivamente Ãs populaÃÃes de Monte Alegre, Prainha e Alenquer. No geral, todas as freqÃÃncias alÃlicas nos Ãxons dos genes XRCC1 e XRCC3 e de ausÃncia do gene GSTM1 foram estatisticamente semelhantes entre os trÃs municÃpios e se mostraram em concordÃncia com freqÃÃncias obtidas em outros estudos com populaÃÃes brasileiras. Conclui-se que, dentre as populaÃÃes estudadas, nÃo houve aumento da incidÃncia de dano ao DNA pela exposiÃÃo ao urÃnio, o que pode se explicar pela baixa radiaÃÃo nessas localidades. AlÃm disso, as freqÃÃncias alÃlicas dos polimorfismos encontrados nos genes de reparo XRCC1 e XRCC3, assim como as de ausÃncia do gene de metabolizaÃÃo GSTM1 nÃo diferiram das encontradas em populaÃÃes de outras regiÃes do Brasil. Desse modo, nas regiÃes estudadas, possivelmente nÃo existe tendÃncia ao desenvolvimento de cÃncer induzido pela exposiÃÃo ao urÃnio. === Radiation is considered a risk factor for the development of several types of cancers caused by damage into the DNA molecule and is of extreme importance, therefore, the monitoring of human populations exposed to it. The municipality of Monte Alegre in the state of Parà in Brazil has one of the largest uranium mining areas of the world, which extends to the neighboring municipalities of Prainha and Alenquer. This work assessed the genotoxic potential of exposure to uranium in rocks found in dwellings in individuals from the municipalities of Monte Alegre, Prainha and Alenquer through the alkaline comet assay in peripheral blood lymphocytes and the determination of the frequencies of polymorphisms in DNA repair genes XRCC1 and XRCC3 and in carcinogen-metabolism gene GSTM1 through direct DNA sequencing. The analysis of the alkaline comet assay indicated that there was no statistically significant difference between the Damage Indexes (DIs) of Monte Alegre (DI = 32.01  1.57), Prainha (DI = 45.80  1.12) and Alenquer (DI = 44.30  0.62) and of the negative control (DI = 42.00  5.75) (p > 0.05). Through direct DNA sequencing, there were polymorphisms in XRCC1 and XRCC3 genes in regions of introns and exons. In XRCC1 gene, the variant allele frequencies for Arg194Trp polymorphism in Monte Alegre, Prainha and Alenquer populations were 12%, 13% and 7%, and for Arg399Gln, 28%, 30% and 32% respectively. In XRCC3 gene, the frequencies of the variant allele of Thr241Met polymorphism found in Monte Alegre, Prainha and Alenquer populations were, respectively, 28%, 13% and 33%. For GSTM1 gene, the frequencies obtained for the absence of this gene were 36%, 31% and 40%, respectively to Monte Alegre, Prainha and Alenquer populations. In general, the absence frequencies of GSTM1 gene and of allelic frequencies in XRCC1 and XRCC3 exons were statistically similar among the three municipalities and were in agreement with frequencies obtained in other studies with Brazilian populations. As a conclusion, among the populations studied, there was no increased incidence of DNA damage by exposure to uranium, which can be explained by the low radiation in these locations and that the allelic frequencies of polymorphisms found in the DNA repair genes XRCC1 and XRCC3, and the absence frequencies of GSTM1 gene did not differ from those in populations from other regions of Brazil. Thus, in the studied area, possibly there is no tendency to the development of cancer induced by exposure to uranium.
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