Changes in pulsatile LH secretion after ovariectomy in Ile-de-France ewes in two seasons

Montgomery, G. W.; Martin, Graeme; Pelletier, J.

doi:10.1530/jrf.0.0730173

Cited by 87 publications

(56 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Despite this minor difference, it appears that the mechanism underlying the effects of season on reproductive activity is the same for both goats and sheep, namely a change in the responsiveness of the hypothalamus to negative feedback by ovarian steroids (review: Karsch et ai, 1984). However, LH secretion in the ovariectomized ewe also appears to be directly affected by photoperiod in the absence of gonadal steroids, an observation which has led to suggestions that steroid-independent pathways are also involved in seasonal reproductive cycles (Goodman et al, 1982;Montgomery et al, 1985). Our data from ovariectomized goats which were not treated with oestradiol suggest that this may not be the case for this species.…”

Section: Methodsmentioning

confidence: 65%

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus)

Chemineau¹,

Martin²,

Saumande³

et al. 1988

Reproduction

Self Cite

View full text Add to dashboard Cite

and 1 month later 6 of them were injected daily (10 h after 'dawn') with 2 mg melatonin. The other 5 animals served as controls. Blood samples (every 10 min for 6h) were taken just before and 38 and 72 days after the start of melatonin treatment. As the experiment progressed, LH pulse frequency increased by 20% in melatonin-treated goats but decreased by 43% in controls. Mean LH values were maintained in melatonin\x=req-\ treated females but decreased in the control group. Melatonin did not affect pulse amplitude.The results of the experiments with ovariectomized does suggest that seasonal reproductive cycles in the goat are caused by changes in the duration of melatonin secretion at night, which induce alterations in the intensity with which oestradiol inhibits LH secretion. In turn, this may be responsibile for the gradual changes in the frequency of LH pulses observed in entire does. The frequency of LH pulses is one of the most important endocrine signals controlling ovarian activity so would form the final link in the chain connecting environmental and reproductive cycles.

show abstract

Section: Methodsmentioning

confidence: 65%

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus)

Chemineau¹,

Martin²,

Saumande³

et al. 1988

Reproduction

Self Cite

View full text Add to dashboard Cite

show abstract

“…Concentrations of LH were measured in duplicate using the RIA method as described by Pelletier et al (1968) and modified by Montgomery et al (1985). The results are expressed as ng ovine LH (batch CY1051 equivalent to 2·5 NIH-LH-S1)/ml.…”

Section: Gonadotrophin Measurementsmentioning

confidence: 99%

Activin and inhibin receptor gene expression in the ewe pituitary throughout the oestrous cycle

Fafioffe

Jf²,

Fontaine³

et al. 2004

Journal of Endocrinology

View full text Add to dashboard Cite

In mammals, activin and inhibin are important regulators of FSH secretion. Previous studies have demonstrated that primary ovine pituitary cells express different activin receptor subtypes: activin receptor-like (ALK)2, ALK4, activin type II receptor A (ActRIIA), ActRIIB and Smad proteins in vitro. Here, we have carried out physiological studies to investigate the pattern of mRNA expression of the activin receptor subunits in the ewe pituitary throughout the oestrous cycle. The oestrous cycles of ewes were synchronized with progestagen sponges. The animals were killed 36 h (before the preovulatory surge, n=4), 48 h (during the preovulatory surge, n=4), 72 h (during the second surge of FSH, n=6) and 192 h (during the luteal phase, n=4) after sponge removal. Using Northern blots, we have shown that the levels of ALK2, ALK4 and ActRIIB mRNA were significantly higher before the preovulatory surge and during the secondary surge of FSH as compared with both during the preovulatory surge and the luteal phase, whereas the level of the ActRIIA mRNA was similar throughout the oestrous cycle. Using Western blots we have also demonstrated that the level of phosphoSmad2 did not vary during the reproductive cycle. Inhibin binding protein (InhBP/p120) and the transforming growth factor-type III receptor, betaglycan, have been identified as putative inhibin co-receptors. In this study, we cloned a fragment of both InhBP/p120 and betaglycan cDNAs in the ewe and showed by Northern blot that pituitary betaglycan and InhBP/p120 mRNA levels did not fluctuate across the oestrous cycle nor did they correlate with serum FSH levels.

show abstract

“…Conversely, during the breeding season oestradiol increases the frequency of LH pulses and reduces pulse amplitude (Karsch, Foster, Bittman & Goodman, 1983). In addition, seasonal changes in LH secretion have been observed in ovariectomized ewes in the absence of exogenous oestrogen (Goodman, Bittman, Foster & Karsch, 1982;Montgomery, Martin & Pelletier, 1985). In ovariectomized Ile-de-France ewes, the frequency of LH pulses varied from one pulse every 35 min during the breeding season to one pulse every 60 min during anoestrus (Montgomery et ai, 1985).…”

Section: Introductionmentioning

confidence: 99%

Gonadotrophin release in ovariectomized ewes fed different amounts of coumestrol

Montgomery¹,

Martin²,

Bars³

et al. 1985

Reproduction

Self Cite

View full text Add to dashboard Cite

Changes in pulsatile LH secretion after ovariectomy in Ile-de-France ewes in two seasons

Cited by 87 publications

References 23 publications

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus)

Seasonal and hormonal control of pulsatile LH secretion in the dairy goat (Capra hircus)

Activin and inhibin receptor gene expression in the ewe pituitary throughout the oestrous cycle

Gonadotrophin release in ovariectomized ewes fed different amounts of coumestrol

Contact Info

Product

Resources

About