Control of the Preovulatory Endocrine Events in the Ewe: Interrelationship of Estradiol, Progesterone, and Luteinizing Hormone*

Karsch, Fred J.; Foster, Douglas L.; Legan, Sandra J.; Ryan, Kathleen D.; Peter, Gregory K.

doi:10.1210/endo-105-2-421

Cited by 98 publications

(66 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The amplitude of LH and FSH surges seen following the first progesterone exposure in this study fell in the lower end of the normal range for intact cyclic ewes (Rawlings et al 1984 (Pant et al 1977;Karsch et al 1979). …”

mentioning

confidence: 47%

“…It has been largely accepted that the demise of the corpus luteum and decrease in progesterone secretion allows a gradual increase in basal LH secretion that stimulates ovarian follicular estradiol Droduction (Karsch et al 1980,1. Increased eitradiol production has been ascribed the role of triggering the preovulatory surges of LH and FSH. Surge releases of LH can be produced in ovariectomized ewes by treating them with implants releasing progesterone and estradiol in patterns mimicking those occurring during a normal estrous cycle (Karsch et al 1979). …”

mentioning

confidence: 99%

See 1 more Smart Citation

Control of the Surge Release of Lh and FSH in Estradiol- And Progesterone-Treated Ovariectomized Ewes

Rawlings¹,

Jeffcoate²,

Currie³

et al. 1988

Can. J. Anim. Sci.

View full text Add to dashboard Cite

show abstract

mentioning

confidence: 47%

mentioning

confidence: 99%

Control of the Surge Release of Lh and FSH in Estradiol- And Progesterone-Treated Ovariectomized Ewes

Rawlings¹,

Jeffcoate²,

Currie³

et al. 1988

Can. J. Anim. Sci.

View full text Add to dashboard Cite

show abstract

“…This postulate is based on the progression of hormonal events that is normally initiated by regression of the corpus luteum and culminates in ovulation during the breeding season (evidence for sequence in Hauger, Legan, Ryan & Peter, 1979). During each oestrous cycle, progesterone is an important steroidal inhibitor of tonic LH secretion, a mode of secretion characterized by discrete pulsatile releases of the gonadotrophin which act upon the ovarian follicle to facilitate the secretion of androgens and oestradiol (Foster, Lemons, Jaffe & Niswender, 1975;Baird, Swanston & Scaramuzzi, 1976;Hauger et al, 1977).…”

Section: Hypothetical Scheme For Feedback Basis Of Seasonal Breedingmentioning

confidence: 99%

Feedback basis of seasonal breeding: test of an hypothesis

Karsch¹,

Goodman²,

Legan³

1980

Reproduction

103

View full text Add to dashboard Cite

It has long been recognized that the seasonal pattern of reproduction in many species is controlled by environmental photoperiod (Yeates, 1949;Hafez, 1952;Menaker, 1971;Follett, 1978;Turek & Campbell, 1979). Insight into the mechanisms whereby photoperiodic cues are transduced into endocrine messages which govern gonadal function, however, has been gained more recently. It has been proposed that in ewes this process of transduction includes a marked change in the hypothalamo\p=n-\hypophysialsystem which controls the tonic mode of gonadotrophin secretion (Legan, (Baird, 1978). The rising levels of LH stimulate ovarian oestradiol secretion, and the two hormones increase in a parallel fashion until oestradiol reaches the threshold for eliciting oestrous behaviour and the LH surge which causes ovulation. The parallel rises in LH and oestradiol are sustained, typically continuing for 48-60 h and ending with the preovulatory LH surge. A crucial requisite for this progression of events is a low response to oestradiol

show abstract

“…Similarly to intact ewes (Karsch et al 1979), the mean concentrations of E 2 in most ewes were lower 4 h after the maximum concentrations of the LH surge than at the peak of the LH surge. This suggests that the feedback regulations of the ovary during anoestrus are identical to those during the breeding season.…”

Section: Discussionmentioning

confidence: 68%

“…The secretion of E 2 increases during the follicular phase and this increase is essential for the LH surge (positive feedback). The LH surge occurs only after a period of prolonged exposure to the above threshold concentrations of E 2 (Corker et al 1969, Karsch et al 1973, 1979, Smith et al 1975, Hauger et al 1977. In sheep, the characteristics of the relationship between the preovulatory rise in systemic concentrations of E 2 and the onset of the LH surge, and presumably of GNRH, varies among breeds (Land et al 1976, Cahill et al 1981, Ben Saïd et al 2007.…”

Section: Introductionmentioning

confidence: 99%

Plasma and ovarian oestradiol and the variability in the LH surge induced in ewes by the ram effect

Fabre-Nys¹,

Chanvallon²,

Debus³

et al. 2015

Reproduction

View full text Add to dashboard Cite

The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable mainly due to whether an LH surge is induced. The aim of this study was to determine the role of oestradiol (E 2 ) in the ram-induced LH surge. In one study, we measured the plasma concentrations of E 2 in ewes of different breeds before and after the 'ram effect' and related these patterns to the presence and latency of the LH surge, while another compared ovarian responses with the 'ram effect' following exposure to rams for 2 or 12 h. In all ewes, the concentration of E 2 increased 2-4 h after rams were introduced and remained elevated for 14.5G0.86 h. The quantity of E 2 secreted before the LH surge varied among breeds as did the mean concentration of E 2 . The granulosa cells of IF ewes collected after 12 h exposure to rams secreted more E2 and progesterone and had higher levels of StAR than the 2 h group but in MV ewes there was no differences between these groups for any of these parameters. These results demonstrate that the LH surge induced by the rams is a result of increased E 2 secretion associated with increased levels of STAR in granulosa cells and that these responses varied among breeds. The results suggest that the variable occurrence of a LH surge and ovulation may be the result of variable ovarian responses to the 'ram effect' and insensitivity of the hypothalamus to the E 2 -positive feedback signal. Free French abstract: A French translation of this abstract is freely available at

show abstract

Control of the Preovulatory Endocrine Events in the Ewe: Interrelationship of Estradiol, Progesterone, and Luteinizing Hormone*

Cited by 98 publications

References 29 publications

Control of the Surge Release of Lh and FSH in Estradiol- And Progesterone-Treated Ovariectomized Ewes

Control of the Surge Release of Lh and FSH in Estradiol- And Progesterone-Treated Ovariectomized Ewes

Feedback basis of seasonal breeding: test of an hypothesis

Plasma and ovarian oestradiol and the variability in the LH surge induced in ewes by the ram effect

Contact Info

Product

Resources

About