The influence of maternal hypothyroidism and radioactive iodine on rat embryonal development: Thyroid C‐cells

Abstract

There have been no works devoted to the study of the influence of 131 I and maternal 131 I-induced hypothyroidism on the state of the C-cells in the thyroid gland of the developing embryos. A study was made on the effect of a dose of 150 µCi 131 I (0.5 Gy) leading to hypothyroidism in rats, on 35 mother rats and 168 newborn pups. The mother rats were divided into control and four treated groups which were injected with 131 I before pregnancy, on gestation days 5, 10, and 16, respectively. Immunohistochemically, the thyroid gland was examined for calcitonin-positive cells. Maternal hypothy-roidism induced by 131 I leads to the development of hyperplasia and hyperthrophy of calcitonin-positive cells in the pups at the time of birth. The discovery of separate C-cells in the peripheral zone of the thyroid lobe may be evidence of an unbalance in the development of the medial and lateral source of the thyroid. There is a verifiable increase in the quantity of C-cells per 1 mm 2 field of the localization in the central zone of the gestation days 10 and 16 groups. This might be a compensatory mechanism for regulating the activity of the thyroid gland under induced hypothyroidism. Thus, in cases when there is a breakdown in the normal external regulation of the embryonic morphogenesis, a reduction in the level of maternal thyroid hormones and also direct exposure to 131 I, there is also a change in the foetus' internal regulatory systems. A change in C-cell system could lead to the appearance of endocrinological disorders later in life. Anat Rec 256:7-13, 1999.

C cells evolve at the same rhythm as follicular cells when thyroidal status changes in rats

“…We have reviewed the literature, both in humans and experimental animals, describing C-cell behaviour in different pathological states of the thyroid gland, but the data are conflicting. In some cases of induced hypothyroidism in rats, a C-cell hyperplasia is described (Peng et al 1975;Stoll et al 1978;Usenko et al 1999), but opposing results are also reported (Bugnon et al 1978;Logonder-Mlinsek et al 1985;Zbucki et al 2007). Similarly, in human pathology, C-cell hyperplastic changes, as well as opposing findings, have been reported in both hypothyroid and hyperthyroid states (Dhillon et al 1982;Scheuba et al 2000;Dadan et al 2001).…”

Experimental Models of the Hypothyroidism

“…С помощью этой модели были воспроизведены такие изменения, которые соответствовали врожденному гипотиреозу у человека, то есть атрофия клеток и снижение массы головного мозга, а также изменения массы тела в потомстве животных [18]. Другие находки включают важные изменения в щитовидной железе у крыс, а именно повреждения клеток щитовидной железы, уменьшение толщины стенок кровеносных сосудов, сильные воспалительные реакции и некротизирование фолликулярных клеток железы [19], а также гиперплазии и гипотрофии клеток, положительных к кальцитонину [19][20]. Достоинством модели является использование небольшого количества радиоактивного йода для развития дисфункции и деструкции щитовидной железы, приводящей к гипотиреозу.…”

Exposure to non-ionizing radiation provokes changes in rat thyroid morphology and expression of HSP-90

“…Hypothyroidism, for example, is characterized by decreased numbers of parafollicular cells, 48 but hypothyroidism in expectant mothers has been found to cause an increase in the size of parafollicular cells in newborns. 49 Harmful environmental effects due to microgravity or hypergravity in outer space are known to provoke a decrease in the number of parafollicular cells, 50 while low frequency EMFs increase their numbers. 45 In the present experiment, exposure of rat thyroid gland to RF at 2.45 GHz and 0.102 AE 12.10 -3 SAR increased HSP-90 marking in the parafollicular cells.…”