Data/hora: 01/06/2024 04:57:42

Biblioteca(s): | Embrapa Caprinos e Ovinos.
Data corrente: | 06/11/2002
Data da última atualização: | 06/11/2002
Autoria: | DALEY, C. A.; SAKURAI, H.; ADAMS, B. M.; ADAMS, T. E.
Título: | Effect of stress-like concentrations of cortisol on gonadotroph function in orchidectomized sheep.
Ano de publicação: | 1999
Fonte/Imprenta: | Biology of Reproduction, v. 60, n. 1, p. 158-163, 1999.
Idioma: | Inglês
Conteúdo: | The effect of stress-like concentrations of cortisol (C) on the feedback potency of estradiol (E,) was assessed using 32 orchidectomized sheep (wethers) assigned at random to 1 of 4 treatment groups in a 2 x 2 factorial design. Wethers received C (3.6 mg/50 kg per hour; groups 2 and 4) or a comparable volume of C delivery vehicle (groups 1 and 3) as a continuous infusion for 7 days. During the final 48 h of infusion, wethers received E2 (0.3 ug/50 kg/h; groups 3 and 4) or E2 delivery vehicle (groups 1 and 2). The pattern of LH secretion was assessed during a 4 h period of intensive blood collection beginning 44 h after initiation of E2 infusion. Gonadotroph responsiveness (LH secretion induced by GnRH challenge [500 ng, i.v.]) was determined 48 h after E2 delivery was begun. Although lhe frequency of secretory episodes of LH was not affected (p > 0.05) by infusion of C or E2 alone, LH pulse frequency was significantly decreased in wethers receiving C and E2 in combination. In contrast, neither the magnitude of basal gonadotroph responsiveness nor the extent of E2-dependent augmentation of responsiveness was significantly affected by stress-like concentrations of C. In a second experiment, the effect of C on the magnitude of E2-induced in- crease in pituitary concentration of GnRH receptor and GnRH receptor mRNA was assessed using 32 additional wethers. Continuous infusion of E2 for 48 h increased (p < 0.05) tissue concentrations of GnRH receptor and GnRH receptor mRNA. Con- current delivery of C did not affect (p > 0.05) E2-induced in- crease in GnRH receptor mRNA but significantly reduced the magnitude of the E2-dependent increase in pituitary concentration of GnRH receptor. Collectively, these data indicate that stress-like concentrations of C enhance the negative feedback potency of E2 and reduce estrogen-dependent augmentation of the concentration of GnRH receptor in pituitary tissue.
Palavras-Chave: | Gonadotropina.
Thesagro: | Hormônio; Ovino; Stress.
Thesaurus Nal: | cortisol.
Categoria do assunto: | --
Registro original: | Embrapa Caprinos e Ovinos (CNPC)
Exemplares: | CNPC - (15073-1) - ADC - AP - -- -  -  - v. 60(1) - DIS