Estrogen, but not progesterone, induces the activity of nitric oxide synthase within the medial preoptic area in female rats

Autor(es)

Lima, Fernanda Barbosa ^{[1, 2]} ; Ota, Fabio Honda ^[1] ; Cabral, Fernanda Janlzur ^{[3, 1]} ; Borges, Bruno Del Bianco ^[1] ; Franci, Celso Rodrigues ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Fac Med Ribeirao Preto, BR-14049900 Ribeirao Preto, SP - Brazil

^[2] Univ Fed Santa Catarina, Ctr Ciencias Biol, Florianopolis, SC - Brazil

^[3] Univ Sao Paulo, Inst Ciencias Biomed, BR-05508 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Brain Research; v. 1578, p. 23-29, AUG 26 2014.
• Citações Web of Science: 4

Resumo

The control of gonadotropin-releasing hormone (GnRH) secretion depends on the action of ovarian steroids and several substances, including nitric oxide (NO). NO in the medial preoptic area (MPOA) stimulates the proestrus surge of luteinizing hormone (LH). We studied the effect of estrogen (Tamoxifen-TMX) and progesterone (RU-486) antagonists on mRNA and protein expression of NO synthase (NOS), the enzyme that produces NO, as well as its activity within MPOA. Female rats received s.c. injections of TMX (3 mg/animal) on first and second days of the estrous cycle (9 am), RU-486 (2 mg/animal) on first, second, (8 am and 5 pm) and third days of the estrous cycle (8 am) or oil (controls) and were killed on the third day (5 pm). Real time-PCR and western blotting were performed to study NOS mRNA and protein expressions. The NOS activity was indirectly assessed by measuring the conversion from {[}C-14]-L-arginine into {[}C-14]-L-citrulline. TMX significantly decreased neuronal NOS (nNOS) mRNA expression (90%), and the activity of NOS, but did not alter nNOS protein expression. Also, TMX significantly decreased LH, FSH, estrogen and progesterone plasma levels. RU-486 nor affected NOS mRNA and protein expressions neither the NOS activity in the MPOA, but reduced FSH levels. The nitrergic system in the MPOA can be stimulated by estrogen whereas TMX decreased NOS activity and mRNA expression. In conclusion, the involvement of the nitrergic system in the MPOA to induce the surge of LH on proestrus depends on the estrogen action to stimulate the mRNA-nNOS expression and the activity of nNOS but it does not seem to depend on progesterone action. (C) 2014 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 09/54887-0 - Controle da secrecao de gonadotrofinas em condicao basal e de estresse: estudo de interacao com esteroides adrenais e hormonio liberador de corticotrofina
• Beneficiário: Celso Rodrigues Franci
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 04/09638-9 - Regulação neuroendócrina e efeitos do estresse sobre a função reprodutora feminina
• Beneficiário: Janete Aparecida Anselmo Franci
• Modalidade de apoio: Auxílio à Pesquisa - Temático