Interaction of Estradiol and a Nonsteroidal Follicular Fluid Substance in the Regulation of Gonadotropin Secretion in the Mare

Miller, Kathleen B.; Wesson, James A.; Ginther, O.J.

doi:10.1095/biolreprod24.2.354

Cited by 59 publications

(38 citation statements)

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“…The greater plasma E 2 in the two species is attributable to the presence of two pre-ovulatory follicles in the double ovulators. A negative effect of exogenous E 2 on FSH has been shown in heifers (Miller et al 1981). In the present study, E 2 concentration was not different between single and double ovulators after the peak of the pre-ovulatory surge, but FSH continued to be lower after the peak of the pre-ovulatory FSH surge and during the ascending portion of the periovulatory surge.…”

Section: Discussionsupporting

confidence: 44%

Follicle and hormone dynamics in single versus double ovulating heifers

Palhão¹,

Beg²,

Rodrigues³

et al. 2009

Reproduction

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Follicles R5 mm were ablated at 4 day post-ovulation in heifers to induce a follicular wave, and prostaglandin F 2a was given at day 6 to increase the incidence of double ovulations. Follicle diameters and plasma hormone concentrations were compared between single ovulators (nZ12) and double ovulators (nZ8). In double ovulators, the interval from follicle deviation to the peak of the pre-ovulatory LH surge was shorter (1.9G0.2 vs 2.5G0.2 days; P!0.02) and diameter of the largest pre-ovulatory follicle was smaller (12.2G0.5 vs 13.3G0.3 mm; P!0.02). The LH concentrations of the pre-ovulatory surge did not differ between single and double ovulators for 24 h on each side of the peak. When data were normalised to LH peak, the peak of the pre-ovulatory FSH and oestradiol (E 2 ) surges occurred in synchrony with the peak of LH surge for both groups. Concentration of FSH for 24 h on each side of the peak showed a group effect (P!0.0001) from lower concentration in the double ovulators. A group-by-hour interaction (P!0.008) for E 2 reflected greater concentration in the double ovulators before and at the peak. Results indicated that two pre-ovulatory follicles resulted in an earlier and greater E 2 increase, leading to lower FSH concentration, an earlier LH surge, and ovulation at a smaller diameter. In conclusion, the difference in hormone concentrations during the pre-ovulatory period was an effect rather than a cause of double ovulations.

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Section: Discussionsupporting

confidence: 44%

Follicle and hormone dynamics in single versus double ovulating heifers

Palhão¹,

Beg²,

Rodrigues³

et al. 2009

Reproduction

View full text Add to dashboard Cite

show abstract

“…A negative feedback effect of follicles on FSH secretion in mares has been demonstrated by ovariectomy (Freedman et al, 1979a;Driancourt and Palmer, 1984), administration of follicular fluid (Miller et al, 1979(Miller et al, , 1981Bergfelt andGinther, 1985, 1986), and follicular ablation (Hinrichs et al, 1991;Gastal et al, 1999b). The suppressive effects of follicles on FSH secretion have been attributed to a nonsteroidal, proteinaceous fraction of follicular fluid (Miller et al, 1979) and to oestradiol (Burns and Douglas, 1981; The role of the number of follicles and circulating immunoreactive inhibin in the decrease in plasma FSH concentrations that occurs during development of a follicular wave was studied in mares.…”

Section: Introductionmentioning

confidence: 99%

Effect of number and diameter of follicles on plasma concentrations of inhibin and FSH in mares

Donadeu¹

2001

Reproduction

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“…Follicular products other than estradiol also suppress FSH and may be responsible for the effect observed [3,153,154]. Inhibin is secreted by the dominant and subordinate follicles during the time of follicular deviation and, together with estradiol, has been associated with the suppressive effects involved in follicular selection and dominance [139,155].…”

Section: Discussionmentioning

confidence: 99%

Effects of a non-steroidal aromatase inhibitor on ovarian function in cattle

Yapura

Mapletoft

Singh

et al. 2012

Reprod. Fertil. Dev.

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Two studies were designed to characterize the effects of a non-steroidal aromatase inhibitor, letrozole, on ovarian function in cattle. The specific objective was to test the hypothesis that letrozole will arrest dominant follicle growth resulting in emergence of a new follicular wave at a predictable interval post-treatment. In a first experiment, postpubertal beef heifers were assigned randomly to four treatment groups and given phosphate-buffered saline (controls; n=10), or letrozole at a dose of 500 (n=9), 250 (n=10), or 125 (n=10) µg/kg intravenously 4 days after follicular ablation (~2.5 days after wave emergence). In a second study, postpubertal beef heifers were assigned randomly to four treatment groups. One group received no treatment (control; n=17) and the other groups (n=9-10) were given 85 µg/kg of letrozole per day (250 µg/kg total dose), from Days 1 to 3, Days 3 to 5, or Days 5 to 7 (Day 0 = pre-treatment ovulation,) corresponding to the periods before, during and after selection of the dominant follicle, respectively. Follicular dynamics were monitored ultrasonically and blood samples were collected for endocrine assays. Follicle diameter profiles and plasma LH, FSH, and estradiol concentrations were analyzed. Additionally, during the second trial, CL diameter profiles and plasma progesterone concentrations were measured. In both studies, the diameter profile of the dominant follicle was larger in heifers treated with letrozole than in control heifers (P<0.05) and the intervals to new wave emergence and onset of regression of the extant dominant follicle were longer (P<0.05) in heifers treated with letrozole than in controls, regardless of the dose (high, medium, or low; single vs multiple) and the stage of the follicle wave in which treatments were initiated. Furthermore, during the second experiment, the mean CL diameter was larger in letrozole-treated heifers, although there were no differences in plasma progesterone iii concentrations between treated and control animals. The effects on dominant follicle and CL diameter profiles appeared to be the result of the significantly increased plasma LH concentrations observed in letrozole-treated animals during both treatment approaches (single vs multiple dose). Incomplete and inconsistent inhibition of estradiol production and the lack of a surge on FSH observed in both experiments may be a result of insufficient circulating levels of letrozole during the treatment period. In summary, a single or multiple dose of letrozole did not induce regression of the extant dominant follicle, nor did it directly affect FSH release.Conversely, letrozole extended the lifespan of the dominant follicle, in association with increased endogenous levels of LH, thereby delaying the next FSH surge and subsequent follicular wave emergence. Results suggest that letrozole has potential as a non-steroidal method for controlling ovarian function in cattle, but further studies are warranted to clarify dosage and timing of treatment to predictably affect follicular wa...

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Interaction of Estradiol and a Nonsteroidal Follicular Fluid Substance in the Regulation of Gonadotropin Secretion in the Mare

Abstract: During the estrous cycle of the mare and several other species, the time of maximum

Cited by 59 publications

References 0 publications

Follicle and hormone dynamics in single versus double ovulating heifers

Follicle and hormone dynamics in single versus double ovulating heifers

Effect of number and diameter of follicles on plasma concentrations of inhibin and FSH in mares

Effects of a non-steroidal aromatase inhibitor on ovarian function in cattle

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