The purpose of this study was to determine the content of iodine and selenium in the thyroid and pituitary glands of rats under iodine-induced blockade of the thyroid gland. Electron probe microanalysis, wavelength-dispersive spectrometry, and point analysis were used in this investigation. We also determined the expression of sodium iodide symporter and caspase 32 in the thyroid and pituitary glands and the expression of thyroid-stimulating hormone in the pituitary. The samples for iodine analysis must be thoroughly dehydrated, and for this purpose, we developed a method that produced samples of constant mass with minimal loss of substrate (human thyroid gland was used for the investigation). Normal levels of iodine and selenium were found in the thyroid, pituitary, ovaries, testes hypothalamus, and pancreas of healthy rats. The levels of iodine and selenium in I- or Se-positive points and the percentage of positive points in most of these organs were similar to those of controls (basal level), except for the level of iodine in the thyroid gland and testes. Blockade of the thyroid gland changed the iodine level in iodine-positive points of the thyroid and the pituitary glands. On the sixth day of blockage, the iodine level in iodine-positive points of the thyroid gradually decreased to the basal level followed by an abrupt increase on the seventh day, implying a rebound effect. The opposite was found in the pituitary, in which the level of iodine in iodine-positive points increased during the first 6 days and then abruptly decreased on the seventh day. Expression of the thyroid-stimulating hormone in the pituitary decreased during the first 5 days but sharply increased on the sixth day, with a minimum level of iodine in the thyroid and maximum in the pituitary, before normalization of the iodine level in both glands preceding the rebound effect. The expression of sodium iodide symporter increased during the first 4 days of blockage and then decreased in both glands. The fluctuations of the thyroid-stimulating hormone in the pituitary gland reflected the changes of iodine in the thyroid gland more precisely than the changes of sodium iodide symporter. The selenium level in the selenium-positive points changed only in the pituitary, dropping to zero on the second and fifth day of the blockade. Simultaneously, the maximum induction of caspase 32 was observed in the pituitary gland. We believe that these results may help to clarify a role of the pituitary gland in the thyroid blockade.

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The purpose of this study was to determine the contents of iodine and selenium in the thyroid, pituitary, adrenal glands and ovaries of female rats under the influence of propylthiouracil (PTU) and the effects of a single dose of potassium iodide (KI) administered two days after the administration of PTU. For the analyses, electron probe microanalysis (EPMA), wavelengthdispersive spectrometry (WDs) and point analysis were used in this study. Ninety-six hours after the first PTU administration the thyroid gland iodine level decreased three-fold in iodide positive points (I-PPs) and the percentage of positive points (%I-PPs) fell by one half. Administration of a single dose of potassium iodide slightly increased the iodine level in I-PPs and restored %I-PPs to the control level. After PTU administration the selenium positive points (Se-PPs) in the thyroid gland decreased by one half, but KI did not help to level these changes. In ovaries, pituitary and adrenal glands PTU administration did not significantly alter the average levels of iodine and selenium, but the Se-PPs and % I-PPs varied over a wide range. Administration of KI restored the levels of iodine and selenium in the pituitary and adrenal glands, but worsened the changes of iodine in ovaries.