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Biblioteca(s):  Embrapa Caprinos e Ovinos.
Data corrente:  22/06/2017
Data da última atualização:  22/06/2017
Autoria:  CLARKE, I. J.; CUMMINS, J. T.; CROWDER, M. E.; NETT, T. M.
Título:  Long-term negative feedback effects of oestrogen and progesterone on the pituitary gland of the long-term ovariectomized ewe.
Ano de publicação:  1989
Fonte/Imprenta:  Journal of Endocrinology, v. 120, n. 2, p. 207-214, Feb. 1989.
DOI:  10.1677/joe.0.1200207
Idioma:  Inglês
Conteúdo:  Abstract: The effects of long-term treatment with physiological doses of oestradiol or oestradiol plus progesterone on plasma gonadotrophin levels and pituitary content of LH and gonadotrophin-releasing hormone (GnRH) receptors were studied in ovariectomized-hypothalamo-pituitary disconnected ewes given 250 ng pulses of GnRH every 2 h (i.v.). A pilot experiment showed that 3 cm long Silastic implants (s.c.) reduced both LH pulse frequency and pulse amplitude in long-term (greater than 6 months) ovariectomized ewes. The main experiment was conducted over 3 weeks in ovariectomized-hypothalamo-pituitary disconnected ewes that had received pulsatile GnRH replacement for 1 week after pituitary surgery. Group 1 (n = 5) received GnRH pulses alone throughout the study. Group 2 (n = 6) received oestradiol in week 2 and oestradiol plus progesterone in week 3 and in group 3 (n = 6) the steroid treatments were reversed. Oestradiol reduced (P less than 0.05) the mean (+/- S.E.M.) amplitude of LH in pulses in group 2 (from 8.2 +/- 1.6 to 5.0 +/- 0.5 micrograms/l) and group 3 (from 11.6 +/- 1.2 to 9.3 +/- 1.0 micrograms 1): an additional effect of progesterone was seen in group 2 but not group 3. The amplitudes of the LH pulses did not change in the control ewes. Plasma concentrations of FSH were reduced by approximately 50% by the oestradiol treatments with no additional effects of progesterone. There was no effect of steroidal treatment on pituitary content of LH or pituitary levels of G... Mostrar Tudo
Palavras-Chave:  FSH; LH; LHRH; Releasing hormones.
Thesagro:  Estradiol.
Thesaurus Nal:  Ewes; Hormone receptors; ovariectomy; Pharmacology; Physiology; Pituitary Hormones; Sheep.
Categoria do assunto:  L Ciência Animal e Produtos de Origem Animal
Marc:  Mostrar Marc Completo
Registro original:  Embrapa Caprinos e Ovinos (CNPC)
Biblioteca ID Origem Tipo/Formato Classificação Cutter Registro Volume Status URL
CNPC33898 - 1ADDAP - PP
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