Effects of Testosterone, Dihydrotestosterone and Estradiol on Gonadotropin Release After Gonadotropin Releasing Hormone Administration in Cyclic Mares

Thompson, Donald L.; Reville-Moroz, S. I.; Derrick, D. J.; Walker, Michael P.

doi:10.1095/biolreprod29.4.970

Cited by 28 publications

(10 citation statements)

References 16 publications

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“…Thompson et al, 1983;Wiest et al, 1987). Plasma concentrations of FSH decreased (P < 0.05) and immunoreactive inhibin concentrations increased (P < 0.05) after day 0 in the follicle-retained groups.…”

Section: Introductionmentioning

confidence: 91%

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

Donadeu¹,

Ginther²

2001

Reproduction

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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. All follicles > or = 6 mm in diameter were ablated by ultrasound-guided transvaginal aspiration of follicular fluid on day 10 after ovulation. During the subsequent wave, all follicles, the three largest follicles (three follicle group), the largest follicle (single follicle group) or no follicles were retained and the remaining follicles were ablated before they reached > 10 mm in diameter (n = 10-11 mares per group). Ablation of new follicles was continued until the day on which the largest follicle of the new wave reached 25 mm in diameter (day 18 after ovulation in the 'no follicle' group). Diameters of retained follicles were measured once a day by transrectal ultrasonography. Plasma samples were taken once a day and analysed by radioimmunoassay for concentrations of FSH and immunoreactive inhibin (includes dimeric inhibin as well as free alpha-subunit forms). Data were normalized to the day of the expected start of the decrease in plasma FSH concentrations (day 0: largest follicle 13 mm in diameter in the follicle-retained groups). A simultaneous increase in circulating concentrations of FSH (P < 0.05) and immunoreactive inhibin (P < 0.05) occurred before the largest follicle reached 13 mm in diameter, which indicates that immunoreactive inhibin produced by follicles < 13 mm in diameter did not suppress FSH. Plasma concentrations of FSH decreased (P < 0.05) and immunoreactive inhibin concentrations increased (P < 0.05) after day 0 in the follicle-retained groups. A slower decrease in FSH concentrations was associated temporally with a delay in the increase in immunoreactive inhibin concentrations in the 'single follicle' group relative to the 'three follicle' and 'all follicle' groups. All follicle-retained groups had similar plasma concentrations of FSH and immunoreactive inhibin after the expected beginning of deviation in growth rates between the two largest follicles (largest follicle 22-23 mm in diameter). These results indicated that the decrease in plasma FSH concentrations from the start of the decrease until the expected day of deviation was a function of multiple follicles of a wave and was attributable to the secretion of inhibin. Thereafter, the largest follicle alone accounted for the continued FSH suppression.

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Section: Introductionmentioning

confidence: 91%

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

Donadeu¹,

Ginther²

2001

Reproduction

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“…In an in vitro study with anterior pituitary cells, E2 did not stimulate LH release directly but increased the GnRH-stimulated release of LH [15]. However, in vivo treatment with E2 did not affect the LH response to GnRH [20,21]. An injection of E2 near the beginning of estrus resulted in an increase in LH concentration [22].…”

Section: Introductionmentioning

confidence: 99%

Negative Effect of Estradiol on Luteinizing Hormone Throughout the Ovulatory Luteinizing Hormone Surge in Mares1

Ginther

Utt²,

Beg

et al. 2007

Biology of Reproduction

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The negative effect of estradiol-17beta (E2) on LH, based on exogenous E2 treatments, and the reciprocal effect of LH on endogenous E2, based on hCG treatments, were studied throughout the ovulatory follicular wave during a total of 103 equine estrous cycles in seven experiments. An initial study developed E2 treatment protocols that approximated physiologic E2 concentrations during the estrous cycle. On Day 13 (ovulation = Day 0), when basal concentrations of E2 and LH precede the ovulatory surges, exogenous E2 significantly depressed LH concentrations to below basal levels. Ablation of all follicles > or = 10 mm when the largest was > or =20 mm resulted in an increase in percentage change in LH concentration within 8 h that was greater (P < 0.03) than for controls or E2-treated/follicle-ablated mares. Significant decreases in LH occurred when E2 was given when the largest follicle was either > or =25 mm, > or =28 mm, > or =35 mm, or near ovulation. Treatment with 200 or 2000 IU of hCG did not affect E2 concentrations during the initial portion of the LH surge (largest follicle, > or =25 mm), but 2000 IU significantly depressed E2 concentrations before ovulation (largest follicle, > or =35 mm). Results indicated a continuous negative effect of E2 on LH throughout the ovulatory follicular wave and may be related to the long LH surge and the long follicular phase in mares. Results also indicated that a reciprocal negative effect of LH on E2 does not develop until the E2 surge reaches a peak.

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“…Thereafter, the largest follicle alone accounted for the continued FSH suppression. Thompson et al, 1983;Wiest et al, 1987). The involvement of oestradiol in the suppression of circulating FSH concentrations in mares has been demonstrated in association with follicle deviation (Gastal et al, 1999a,b).…”

Section: Introductionmentioning

confidence: 99%

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

Donadeu¹

2001

Reproduction

View full text Add to dashboard Cite

Effects of Testosterone, Dihydrotestosterone and Estradiol on Gonadotropin Release After Gonadotropin Releasing Hormone Administration in Cyclic Mares

Cited by 28 publications

References 16 publications

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

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

Negative Effect of Estradiol on Luteinizing Hormone Throughout the Ovulatory Luteinizing Hormone Surge in Mares1

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

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