Document Detail


Effects of pregnancy on pulsatile secretion of LH and gonadotrophin-releasing hormone-induced LH release in sheep: a longitudinal study.
MedLine Citation:
PMID:  12611598     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Pulsatile LH secretion and its control throughout pregnancy have not been fully determined in sheep. Expt 1 determined the patterns of LH secretion in five ewes on days 10, 20, 60 and 120 of pregnancy and on day 10 postpartum, compared with those on day 10 of the oestrous cycle. Mean (+/- SEM) concentrations of LH declined steadily throughout pregnancy (ANOVA, P < 0.01) and were lower (P < 0.01) on day 60 (0.19 +/- 0.3 ng ml(-1)) and on day 120 (0.18 +/- 0.4 ng ml(-1)) of pregnancy than on day 10 of the oestrous cycle (0.55 +/- 0.04 ng ml(-1)). This decrease was due to a significant reduction in the number and the amplitude of LH pulses. Only on day 120 of pregnancy were progesterone concentrations higher (P < 0.01) than on day 10 of the oestrous cycle. Although concentrations of progesterone on day 10 postpartum were barely detectable, mean LH concentration (0.45 +/- 0.09 ng ml(-1)) was not different from that on day 10 of the oestrous cycle. Expt 2 examined the LH responses in a separate group of four ewes to a physiological dose of GnRH (0.2 microg) on days 10, 20, 60 and 120 of pregnancy and on day 10 postpartum, compared with those on day 10 of the oestrous cycle. The area under the LH response curve and the maximum LH concentrations induced by GnRH declined steadily throughout pregnancy (ANOVA, P < 0.01) and were lower (P < 0.01) on days 60 and 120 of pregnancy than on day 10 of the oestrous cycle, but these parameters were not different between day 10 postpartum and day 10 of the oestrous cycle. Expt 3 examined the LH responses in a separate group of four ewes to a potent GnRH agonist, buserelin (0.5 microg), on days 10, 60 and 120 of pregnancy. The area under the LH response curve and the maximum LH concentrations induced by GnRH were lower (P < 0.01) on days 60 and 120 than on day 10 of pregnancy, but were not different between days 60 and 120. This longitudinal study demonstrates that the pulsatile LH release and pituitary responsiveness to GnRH decreases progressively as pregnancy advances, but does not support the hypothesis that high concentrations of progesterone are solely responsible for the inhibition of pulsatile LH secretion and GnRH-induced LH release during pregnancy in sheep.
Authors:
K H Al-Gubory; J Hervieu; P A Fowler
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Reproduction (Cambridge, England)     Volume:  125     ISSN:  1470-1626     ISO Abbreviation:  Reproduction     Publication Date:  2003 Mar 
Date Detail:
Created Date:  2003-03-03     Completed Date:  2003-06-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  100966036     Medline TA:  Reproduction     Country:  England    
Other Details:
Languages:  eng     Pagination:  347-55     Citation Subset:  IM    
Affiliation:
Unité de Recherches de Physiologie Animale, 78352 Jouy-en-Josas Cedex, France. algubory@jouy.inra.fr
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MeSH Terms
Descriptor/Qualifier:
Animals
Area Under Curve
Buserelin / pharmacology
Dose-Response Relationship, Drug
Female
Gestational Age
Gonadotropin-Releasing Hormone / pharmacology*
Luteal Phase / blood
Luteinizing Hormone / blood,  secretion*
Pituitary Gland / drug effects*
Postpartum Period / blood
Pregnancy
Pregnancy, Animal / blood*
Progesterone / blood
Secretory Rate
Sheep / physiology*
Chemical
Reg. No./Substance:
33515-09-2/Gonadotropin-Releasing Hormone; 57-83-0/Progesterone; 57982-77-1/Buserelin; 9002-67-9/Luteinizing Hormone

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