Features of radiation and chemical effects on the thyroid gland of small mammals

At present, there is an acute problem of assessing multifactorial anthropogenic impacts on animal populations. The ability of toxicants to move considerable distances from the source of pollution and the unpredictability of their combined action require a more detailed study of the formation of effects when factors enter the mammalian body for a long time. The thyroid gland plays an essential role in the adaptation of the body to constantly changing environmental conditions. At that, it is labile and responds to anthropogenic transformation of the environment by changing the structural and functional characteristics of its components. The aim of the study is to investigate the features of the chronic effect of radiation and chemical factors on the formation of the thyroid response in mice and to determine the morphological criteria of thyroid tissue, by which it is possible to assess the nature of such effects in mammals living in technogenically polluted territories. Experiments were conducted on mature male mice of the NEA line, first the effects of the separate action of factors were studied, and then the variants of their joint action. The animals were exposed to gamma irradiation for 30 days (226Ra) at an exposure dose rate of 2000-2500 µR/h (1.6 sGr ). Mice also received sodium nitrate orally for 30 days at concentrations of 10 and 45 mg/l. Using morphological research methods, it was estimated that the thyroid gland of mice was highly sensitive to chronic low-intensity gamma irradiation and sodium nitrate in doses and concentrations actually occurring in the environment. This allows us to propose indicators of its morphofunctional state for use as a criterion for assessing the biological effect of radiation and chemical effects. The combined effect of the studied factors had a greater effect on the thyroid parenchyma compared to their separate action. The results obtained should be taken into account when assessing multifactorial anthropogenic impacts on the mammalian thyroid gland and with the environmental regulation of man-made load on terrestrial ecosystems.