Selenium in the anterior pituitary of rats exposed to sodium selenite: light and electron microscopic localization.

Metal selenide accumulations were demonstrated in the anterior pituitary of the rat by a histochemical technique at light and electron microscopic levels. After administration of sodium selenite either by drinking water (2.5 to 15 ppm) or by ip injection (5 to 20 mg/kg body wt), intracellular accumulations were found in secretory granules and lysosomes of the somatotrophs, thyrotrophs, corticotrophs, and the gonadotrophs. The amount of countable deposits increased with increasing doses, whether selenite was given in drinking water or by ip injection. Localization of deposits was independent of route of administration. Following a single ip injection of 5 mg sodium selenite/kg, a steadily increasing amount of visible deposits was seen throughout the first week. After this peak the deposits started to decrease but could still be found after 2 weeks. Selenium may possibly create bonds to endogenous zinc in the anterior pituitary as has been suggested for the brain.