Virchows Archiv B Cell Pathol (1990) 59:291-296 Virchows Archiv B Cell Pathology Including Molecular Patlmiogy 9 Springer-Verlag 1990 Selenium complexes in the anterior pituitary of rats exposed to L-selenomethionine Henning Gronb~ek and Ole Thorlacius-Ussing Department of Neurobiology, Institute of Anatomy, University of Aarhus, DK-8000 Aarhus C, Denmark Received April 7 / Accepted July 27, 1990 Summary. Selenium precipitates were demonstrated Selenium precipitates were demonstrated histochemically by silver amplification at light and electron microscopic levels in the anterior pituitary of rats exposed to L-selenomethionine (SeMeth). By electron microscopy (EM), the silver amplified selenium complexes were identified in somatotrophs, corticotrophs and gonadotrophs. Precipitates were observed mainly in the secretory granules and to a lesser extent in the lysosomes. The staining intensity increased with increasing amounts of SeMeth. Following a single injection of 3.7 mg Se/kg a substantial increase in staining was observed during the first 48 h after injection and precipitates could still be observed in the anterior pituitary after 2 weeks. During a long-term study where the rats were exposed to selenium contained in the drinking water (3.0 mg Se/1 drinking water for 1, 2 or 4 weeks) an increasing amount of precipitates were observed during the first 2 weeks followed by a small decrease in staining intensity. Organic selenium, or rather a metabolite, is suggested to form bands with endogenous metal, primarily zinc, as has been suggested in the brain and anterior pituitary after exposure to sodium selenite. Key words: Selenium - L-Selenomethionine - Anterior Selenium - L-Selenomethionine - Anterior pituitary - Rat Introduction Schoentall (1968) demonstrated that selenium accumulates in the rat anterior pituitary after a subcutaneous injection of radioactive labelled 75-Se sodium selenite. It has also been shown that both the rat and human anterior pituitary contains large amounts of selenium (Merriam et al. 1979; Thorlacius-Ussing 1987; Thorlacius- Ussing et al. 1988a). In previous studies using radioisotopes of 75-Se sodium selenite and SeMeth, we have observed that selenium accumulates in large Offprint requests to: H. Gronb~ek H. Gronb~ek amounts in the anterior pituitary of rats after intraperitoneal as well as oral administration (Thorlacius-Ussing and Jensen 1988; Gronb~ek and Thorlacius-Ussing 1988). Earlier studies have correlated this selenium accumulation in the anterior pituitary to endocrine dysfunction in selenium-intoxicated animals (Jensen 1975; Glover et al. 1979). Recent results from our laboratory have demonstrated a substantial decrease in growth hormone secretion from the anterior pituitary as well as a decrease in somatomedin C production in young rats exposed to sodium selenite (Thorlacius-Ussing et al. 1987, 1988b, c). In a previous study using a histochemical technique, selenium complexes were demonstrated particularly in growth hormone-producing cells in the anterior pituitary of rats exposed to sodium selenite (Thorlacius-Ussing and Danscher 1985). This histochemical method demonstrates complexes of exogenous selenium and endogenous metal. In the central nervous system and the anterior pituitary, selenium is suggested to form bonds with zinc (Danscher 1984; Thorlacius-Ussing 1987). The metabolism of organic and inorganic selenium is different (Ip 1988). The aim of the present study was to demonstrate stained selenium complexes by light and electron microscopy in the anterior pituitary of rats exposed to organic selenium, since previous studies have demonstrated such complexes in rats exposed to inorganic selenium. Material and methods For this study we used 32 male Wistar rats, divided in two groups and exposed to SeMeth according to Tables 1 and 2. All the animals had free access to stock pellets (Altromin 1324, Altromin Specialfutterwerke, GMBH) with a declared content of 0.2 ppm selenium as sodium selenite. Using a fluorometric method (Thorling et al. 1985) the selenium content in the pellets was checked. In group A, (n= 18), 12 rats were given intraperitoneal injections of SeMeth (1.5 mg Se/kg body weight) and were allowed to survive for between 1 h and 14 days. The remaining six rats...
Selenium in Biology and Medicine, 1990, p. 130-132