Estradiol reduces cumulative mercury and associated disturbances in the hypothalamus-pituitary axis of ovariectomized rats.
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.
Oliveira
Fabíola Raquel Tenório
FR
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.
Ferreira
Josione Rêgo
JR
dos Santos
Carlos Maurício Corrêa
CM
Macêdo
Lano Ermenson Miranda
LE
de Oliveira
Ricardo Bezerra
RB
Rodrigues
José Antunes
JA
do Nascimento
José Luiz Martins
JL
Faro
Lílian Rosana Ferreira
LR
Diniz
Domingos Luiz Wanderley Picanço
DL
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
D008767:Methylmercury Compounds; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone; C004925:methylmercuric chloride