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 difference...

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Published in:	Ecotoxicology and environmental safety Vol. 63; no. 3; pp. 488 - 493
Main Authors:	Oliveira, Fabíola Raquel Tenório, Ferreira, Josione Rêgo, dos Santos, Carlos Maurício Corrêa, Macêdo, Lano Ermenson Miranda, de Oliveira, Ricardo Bezerra, Rodrigues, José Antunes, do Nascimento, José Luiz Martins, Faro, Lílian Rosana Ferreira, Diniz, Domingos Luiz Wanderley Picanço
Format:	Journal Article
Language:	English
Published:	San Diego, CA Elsevier Inc 01-03-2006 Elsevier
Subjects:	Administration, Oral Animals Biological and medical sciences Biotransformation Chemical and industrial products toxicology. Toxic occupational diseases Cumulative mercury Dose-Response Relationship, Drug Endocrine disturbances Estradiol Estradiol - pharmacology Estrous Cycle - drug effects Female Gonadotropin-Releasing Hormone - blood Hypothalamo-Hypophyseal System - drug effects Hypothalamo-Hypophyseal System - metabolism Hypothalamus - drug effects Hypothalamus - metabolism Luteinizing Hormone - blood Medical sciences Mercury Poisoning - blood Mercury Poisoning - prevention & control Metals and various inorganic compounds Methylmercury Compounds - pharmacokinetics Methylmercury Compounds - toxicity Ovariectomy Pituitary Gland, Anterior - drug effects Pituitary Gland, Anterior - metabolism Rats Rats, Wistar Toxicology Endocrine disturbances Estradiol Cumulative mercury Hypothalamohypophyseal axis Ecotoxicology Ovariectomy Rat Toxicity Rodentia Endocrine disruptor Perturbation Experimental study Heavy metal Vertebrata Mammalia Environment Poisoning Mercury
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Summary:	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 17 β 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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0147-6513 1090-2414
DOI:	10.1016/j.ecoenv.2004.12.024