Expression of NIS in the thyroid and pituitary of female rats after a single dose of potassium iodide

Abstract

Objective. The aim of this work was to study the expression of NIS in the thyroid and anterior pituitary in rats after a single dose of iodide appropriate to the content of iodide in iodine-positive points in the thyroid and pituitary. Methods. A total of 41 inbred rat females of local laboratory strain weighing 250-300 g at the stage of diestrus and/or metestrus were used. Pituitaries and thyroids were dissected from 15 control rats at the same time as these from four groups of 6-8 rats each which were given various doses of potassium iodide dissolved in 0.5 ml distilled water (6 rats - 1 μg/100 g body weight; 8 rats - 4 μg/100 g; 6 rats - 8 μg/100 g; 6 rats - 25 μg/100 g.) by gavage at 48 h before sacrifice. In 6 rats of control group the concentration of iodine in thyroids and pituitaries was estimated in terms of percent by weight in dry tissue (wt% I-2 dry tissue) using the wavelength dispersive spectrometry (WDS) quantitative analysis. The expression of NIS in thyroids and pituitaries in terms of the percentage of positive immunostained area (% PA) was measured by streptavidin-biotin method using specific polyclonal antibodies. Results. In thyroids, the concentration of iodine in iodine-positive points ranged from 2.5 to 59.3 (mean of 16.7±3.0) in terms of wt% I-2 dry tissue (100 % iodine-positive points), while in pituitaries it ranged from 0.17 to 6.3 (mean of 1.4±0.3) in all points and 2.2±0.4 in iodine-positive points. Histochemical reaction for NIS in the pituitaries at 48 hours after iodide administration showed a dose related increase beginning from 4 μg/100 g (from 1.8±0.7 to 12.9±1.0 % PA, respectively to the dose of iodide), while such increase in the thyroids started from 8 μg/100g (from 3.7±1.2 to 9.1±2.0 % PA). It remained still increased in pituitaries after the dose of 8 μg/100g (11.4±1.0 % PA) and 25 μg/100g (13.9±1.5 % PA), while such increase in thyroids was found only after the dose of 25 μg/100g (11.9±2.8 % PA). Conclusion. It was found that in the pituitaries of rat females the expression of NIS started after the dose of 4 μg iodide/100g, while that in the thyroids started after 8 μg iodide/100g. Thus, it may be suggested that the pituitary appears more susceptible to the level of iodide in blood.