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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 GnRH receptors MenosAbstract: 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: |
LEADER 02373naa a2200313 a 4500 001 2071292 005 2017-06-22 008 1989 bl uuuu u00u1 u #d 024 7 $a10.1677/joe.0.1200207$2DOI 100 1 $aCLARKE, I. J. 245 $aLong-term negative feedback effects of oestrogen and progesterone on the pituitary gland of the long-term ovariectomized ewe. 260 $c1989 520 $aAbstract: 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 GnRH receptors 650 $aEwes 650 $aHormone receptors 650 $aovariectomy 650 $aPharmacology 650 $aPhysiology 650 $aPituitary Hormones 650 $aSheep 650 $aEstradiol 653 $aFSH 653 $aLH 653 $aLHRH 653 $aReleasing hormones 700 1 $aCUMMINS, J. T. 700 1 $aCROWDER, M. E. 700 1 $aNETT, T. M. 773 $tJournal of Endocrinology$gv. 120, n. 2, p. 207-214, Feb. 1989.
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