Effect of Suppression of FSH with a GnRH Antagonist (Acyline) Before and During Follicle Deviation in the Mare

Checura, Celina M.; Beg, M.A.; Gastal, E.L.; Gastal, M.O.; Wiltbank, M. C.; Parrish, J.J.; Ginther, O.J.

doi:10.1111/j.1439-0531.2008.01222.x

Cited by 14 publications

(7 citation statements)

References 44 publications

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“…The GnRH antagonist actions of acyline have been demonstrated previously in dogs [42], horses [43], cattle [44], rodents [45], monkeys [46], and humans [47]. The actions of acyline in the present study likely are mediated by reduced LH pulses.…”

Section: Discussionsupporting

confidence: 54%

The Role of Luteinizing Hormone in Regulating Gene Expression During Selection of a Dominant Follicle in Cattle

Luo¹,

Gümen²,

Haughian³

et al. 2010

Biology of Reproduction

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At approximately 8.5 mm in diameter, the future dominant follicle is "selected" for continued growth in cattle. In the present study, cows were treated with a gonadotropin-releasing hormone receptor antagonist, acyline, just before follicle selection (near 7.8 mm) to investigate the role of LH in changing mRNA concentrations during selection of a dominant follicle. The ovaries containing the expected dominant follicle (EDF; first largest follicle) and expected largest subordinate follicle (ESF) were removed after 12 or 24 h of treatment. Real-time PCR was used to determine mRNA concentrations. ELISA was used to measure testosterone and 17beta-estradiol (E(2)) and radioimmunoassay to measure androstenedione (A(4)) in follicular fluid. Concentrations of E(2) were greater in EDF than in ESF of untreated cows near the time of follicle selection (12 h) or at 12 h after selection (24 h). Testosterone, E(2), and A(4) were all dramatically decreased by acyline treatment at both times. In theca cells, acyline treatment reduced CYP17A1 (P450 17alpha) in EDF and STAR (steroidogenic acute regulatory protein) in both EDF and ESF but did not alter CYP11A1 (P450scc). In granulosa cells (GCs), LHCGR (luteinizing hormone [LH] receptor) was much greater in EDF than in ESF at both time of selection (739% greater) and 12 h after selection (2837% greater) and was decreased by acyline in EDF (87% decrease). The mRNA for CYP19A1 (cytochrome P450 aromatase) and PAPPA (pregnancy-associated plasma protein-A) tended to be greater in EDF than in ESF at follicle selection, and both mRNAs were much greater at 12 h after selection, with acyline significantly decreasing PAPPA mRNA after 24 h of treatment. The mRNA for FSHR (follicle-stimulating hormone receptor) was not different in EDF versus ESF and was not altered by acyline. Thus, induction of LHCGR mRNA in GCs is an early event during the follicle selection process, and surprisingly, expression of LHCGR mRNA is dependent on circulating LH. Production of follicular A(4), testosterone, and E(2) are also acutely related to LH but due to changes in expression of STAR and CYP17A1 in TC.

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Section: Discussionsupporting

confidence: 54%

The Role of Luteinizing Hormone in Regulating Gene Expression During Selection of a Dominant Follicle in Cattle

Luo¹,

Gümen²,

Haughian³

et al. 2010

Biology of Reproduction

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“…Acyline is a long-acting antagonist of gonadotropin-releasing hormone (GnRH) receptor [26], which competitively inhibits GnRH action at pituitary receptor sites [27] and suppresses the secretion of gonadotropins. It has been used to suppress LH in cattle [28] and mares [29].…”

Section: Introductionmentioning

confidence: 99%

Role of Luteinizing Hormone in Changes in Concentrations of Progesterone and Luteal Blood Flow During the Hours of a Simulated Pulse of 13,14-Dihydro-15-Keto-Prostaglandin F2alpha (PGFM) in Heifers

Shrestha¹,

Pugliesi

Beg

et al. 2011

Biology of Reproduction

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A bolus treatment (e.g., 25 mg) of prostaglandin F(2alpha) (PGF) in the study of luteolysis in cattle results in dubious interpretations. Therefore, in experiment 1 of the present study, a 13,14-dihydro-15-keto-PGF (PGFM) pulse was simulated by incremental intrauterine (IU) infusion of PGF for 2.7 h on Day 14 postovulation. Concentrations of PGFM during the first hour of infusion and at the maximum were not different between simulated (n = 7) and spontaneous (n = 7) pulses. In experiment 2, four groups (n = 6 per group) were treated at Minute 0 (beginning of infusion) as follows: saline (infused IU), PGF (infused IU), acyline/saline, and acyline/PGF. Two hours before Minute 0, each heifer was given flunixin meglumine to inhibit endogenous PGF secretion, and heifers in the acyline/saline and acyline/PGF groups were given acyline to inhibit luteinizing hormone (LH). Plasma progesterone concentrations were similar among groups during Minutes 0 to 60, with no indication of an initial transient progesterone increase in the two PGF groups. Progesterone began to decrease in the PGF groups at Minute 60 and to rebound at Minute 135 after the PGFM peak at Minute 120. The rebound was complete in association with an increase in LH in the PGF group, but it was not complete when LH was inhibited in the acyline/PGF group. Luteal blood flow increased during PGF infusion in the two PGF groups and remained elevated for approximately 2 h after the PGFM peak in the PGF group but not in the acyline/PGF group. Novel findings were that an initial transient increase in progesterone did not occur with the simulated PGFM pulse and that LH stimulated a progesterone rebound and maintained the elevated luteal blood flow after the PGFM peak.

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“…Gonadotropin-releasing hormone (GnRH) antagonists suppress pituitary gonadotropin secretion by competitive blockade of GnRH receptors [23-25]. Such molecules have been used to study the role of gonadotropins (FSH and LH) in the control of follicular development, ovulation and establishment and maintenance of the CL in several animal species [26-32]. The use of a specific GnRH antagonist that can block the pituitary response to exogenous and endogenous GnRH provides an opportunity to determine, in vivo, whether the OIF-induced preovulatory LH surge is a result of activation of hypothalamic GnRH neurons or a direct effect on the pituitary gland as previously suggested by in vitro studies [18-21].…”

Section: Introductionmentioning

confidence: 99%

Cetrorelix suppresses the preovulatory LH surge and ovulation induced by ovulation-inducing factor (OIF) present in llama seminal plasma

Silva

Smulders

Guerra

et al. 2011

Reprod Biol Endocrinol

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BackgroundThe purpose of the study was to determine if the effect of llama OIF on LH secretion is mediated by stimulation of the hypothalamus or pituitary gland.MethodsUsing a 2-by-2 factorial design to examine the effects of OIF vs GnRH with or without a GnRH antagonist, llamas with a growing ovarian follicle greater than or equal to 8 mm were assigned randomly to four groups (n = 7 per group) and a) pre-treated with 1.5 mg of GnRH antagonist (cetrorelix acetate) followed by 1 mg of purified llama OIF, b) pre-treated with 1.5 mg of cetrorelix followed by 50 micrograms of GnRH, c) pre-treated with a placebo (2 ml of saline) followed by 1 mg of purified llama OIF or d) pre-treated with a placebo (2 ml of saline) followed by 50 micrograms of GnRH. Pre-treatment with cetrorelix or saline was given as a single slow intravenous dose 2 hours before intramuscular administration of either GnRH or OIF. Blood samples for LH measurement were taken every 15 minutes from 1.5 hours before to 8 hours after treatment. The ovaries were examined by ultrasonography to detect ovulation and CL formation. Blood samples for progesterone measurement were taken every-other-day from Day 0 (day of treatment) to Day 16.ResultsOvulation rate was not different (P = 0.89) between placebo+GnRH (86%) and placebo+OIF groups (100%); however, no ovulations were detected in llamas pre-treated with cetrorelix. Plasma LH concentrations surged (P < 0.01) after treatment in both placebo+OIF and placebo+GnRH groups, but not in the cetrorelix groups. Maximum plasma LH concentrations and CL diameter profiles did not differ between the placebo-treated groups, but plasma progesterone concentrations were higher (P < 0.05), on days 6, 8 and 12 after treatment, in the OIF- vs GnRH-treated group.ConclusionCetrorelix (GnRH antagonist) inhibited the preovulatory LH surge induced by OIF in llamas suggesting that LH secretion is modulated by a direct or indirect effect of OIF on GnRH neurons in the hypothalamus.

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Effect of Suppression of FSH with a GnRH Antagonist (Acyline) Before and During Follicle Deviation in the Mare

Cited by 14 publications

References 44 publications

The Role of Luteinizing Hormone in Regulating Gene Expression During Selection of a Dominant Follicle in Cattle

The Role of Luteinizing Hormone in Regulating Gene Expression During Selection of a Dominant Follicle in Cattle

Role of Luteinizing Hormone in Changes in Concentrations of Progesterone and Luteal Blood Flow During the Hours of a Simulated Pulse of 13,14-Dihydro-15-Keto-Prostaglandin F2alpha (PGFM) in Heifers

Cetrorelix suppresses the preovulatory LH surge and ovulation induced by ovulation-inducing factor (OIF) present in llama seminal plasma

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