AVALIAÇÃO DOS EFEITOS DA RADIAÇÃO GAMA SOBRE O DESENVOLVIMENTO DE CÂNCER DE MAMA EM RATAS WISTAR

Abstract

The city of Guarapariis well known for the presence of monazitic sand on its beaches. The monazitic sands present in the sands of Meaípe beach are a source of natural radiation associated with several effects on the health of the inhabitants. However, this is the first scientific study that evaluates the biological effects of radiation from Meaipe beach, as well as the carcinogenic effects of this sand. In this investigation, we evaluated the possible effects of natural radiation (3.61 μSv/h) emitted by the monazite sands of Guarapari, on the development of breast cancer in female Wistar rats, using a gamma radiation physical simulator built with sand taken from the beach of Meaipe. We induced cancer with 7,12-dimethylbenzanthracene (DMBA), administered by gavage in virgin ratsand evaluated body weight, estrous cycle and blood pressure during the experiment. After 26 weeks of cancer induction,we analyzed morphology, inflammation, estrogen levels and oxidative stress. In addition, we identified and classified the lesions in the 4th pair of the mammary gland. Exposure to radiation released by monazite sands showed anthropometric changes in the first two months of experiments in groups exposed to radiation and/or induced to cancer. Radiation did not cause changes in systolic and diastolic blood pressure. All the rats in the study showed all phases of the estrous cycle and the rats exposed to radiation showed small changes in the evaluation of the cycle both at the beginning and at the end. The two groups exposed to radiation had higher circulating estrogen levels and lower collagen deposition in adipose tissue. We did not notice changes in the assessment of inflammation through the number of mast cells, nor changes in oxidative stress assessed by Dihydroethidium (DHE). We observed the abnormal morphological development of the breast, with reduced number of terminal buds (terminal end buds-TEBs), alveolar terminals (AB) and lobules in the breasts of rats induced to cancer without exposure to ionizing radiation. Furthermore, the rats induced to cancer and exposed to ionizing radiation had a lower number of cancerous lesions when compared to the group that was induced to cancer without exposure to radiation. Our data show that the continuous exposure of Wistar rats to natural gamma radiation was able to increase the number of mammary glands without cancerous changes, in addition to preventing the development of lesions classified as cribriform. Thus, new experiments are needed to determine more precisely the beneficial effects of radiation from the sands of Meaipe beach in the prevention of breast cancer.