title: Estradiol reduces cumulative mercury and associated disturbances in the hypothalamus-pituitary axis of ovariectomized rats.
abstract: The aim of this research was to verify the incidence of endocrine dysfunction associated with mercury intoxication in the hypothalamus-pituitary reproductive system of normally cycling or castrated female rats and the possible protective action of estrogen replacement therapy. We found no differences in the frequency of estrus cycle stages (diestrus I, diestrus II, proestrus, and estrus) in normally cycling female rats during 54 days of daily oral administration of 0.004, 0.02, and 1 mg/kg MeHgCl. Conversely, the higher dose (1 mg/kg) induced a significant decrease in content of luteinizing hormone releasing hormone (LHRH) into the medial hypothalamus when administered daily during 3 days in ovariectomized rats. This effect was associated with increased levels of mercury found in the anterior pituitary gland and medial hypothalamus, rather than the anterior and posterior hypothalamus, striatum or cerebellum. A decrease in plasma levels of luteinizing hormone (LH) was also detected after administration of 7.5 mg/kg MeHgCl. These disturbances in LHRH and LH secretion induced by mercury were abolished or superimposed (respectively) by estrogenic replacement therapy (0.025 mg/kg 17beta estradiol cypionate, intramuscular). These effects were associated with a significant reduction in mercury content of the anterior pituitary gland and medial hypothalamus, suggesting a protective estrogenic effect.
authors.affiliation: Laboratory of Neuroendocrinology. Department of Physiology, Biological Sciences Center, Federal University of Pará, Campus do Guama Rua Augusto Correa 1, 66075-110, Belém, Pará, Brazil.
authors.forename: Fabíola Raquel Tenório
authors.initials: FR
authors.lastname: Oliveira
authors.forename: Josione Rêgo
authors.initials: JR
authors.lastname: Ferreira
authors.forename: Carlos Maurício Corrêa
authors.initials: CM
authors.lastname: dos Santos
authors.forename: Lano Ermenson Miranda
authors.initials: LE
authors.lastname: Macêdo
authors.forename: Ricardo Bezerra
authors.initials: RB
authors.lastname: de Oliveira
authors.forename: José Antunes
authors.initials: JA
authors.lastname: Rodrigues
authors.forename: José Luiz Martins
authors.initials: JL
authors.lastname: do Nascimento
authors.forename: Lílian Rosana Ferreira
authors.initials: LR
authors.lastname: Faro
authors.forename: Domingos Luiz Wanderley Picanço
authors.initials: DL
authors.lastname: Diniz
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001711:Biotransformation; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology*; D030762:Estrous Cycle / Q000187:drug effects; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects* / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood; D008630:Mercury Poisoning / Q000097:blood / Q000517:prevention & control*; D008767:Methylmercury Compounds / Q000493:pharmacokinetics / Q000633:toxicity*; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D008767:Methylmercury Compounds; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone; C004925:methylmercuric chloride