LHRH antagonist decreases LH and progesterone secretion but does not alter length of estrous cycle in heifers.

Ülker, Hasan; Gant, B T; Avila, David M. de; Reeves, J.J.

doi:10.2527/2001.79112902x

Cited by 7 publications

(7 citation statements)

References 15 publications

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“…In cattle and sheep, only the preovulatory FSH surge appears to be acutely dependent on GnRH stimulation, with concentrations of circulating FSH during most of the cycle regulated primarily by inhibitory molecules, particularly inhibin and to a lesser extent estrogen, acting directly on the pituitary gland [51]. Thus, acute treatments with a GnRH receptor antagonist do not decrease basal FSH during the normal estrous cycle of cattle [52][53][54]. The decrease in stimulation of theca cells by LH pulses during acyline treatment was expected to decrease androgen concentrations in follicular fluid, as was observed in the present study (Fig.…”

Section: Discussionmentioning

confidence: 86%

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: Discussionmentioning

confidence: 86%

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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“…Pre-treatment with cetrorelix or saline was given as a single slow intravenous dose 2 hours before intramuscular administration of either GnRH or OIF. The dose of cetrorelix (10 μg/Kg of body weight) was based on previous reports of effective suppression of pituitary LH secretion in several animal species [27,31,32]. Treatment with GnRH or OIF was given 2 hours after cetrorelix or placebo administration, based on a previous report that demonstrated rapid blockade of LH secretion after intravenous administration of the GnRH antagonist [34].…”

Section: Methodsmentioning

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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“…The profound effect of the lower dose of BA over the higher one observed in this study may possibly be attributed to the fact that high doses of GnRH may result in reduced storage of LH in the pituitary gland and in decreased numbers of GnRH receptors on pituitary cells, resulting in suppressed gonadotropin secretion from the pituitary gland (Peters et al, 1994;Ulker et al, 2001 andSato et al, 2005).…”

Section: Gonadotrophins (Lh and Fsh)mentioning

confidence: 71%

“…Unlike the other two hormones, however, E 2 in response to high-BA was lower than the other two groups, including control (Fig 3). Whether this was a direct effect of BA on E 2 or an indirect effect mediated through LH (Fig 1) is uncertain; however, high doses of GnRH have been shown to decrease LH (Peters et al, 1994;Ulker et al, 2001 andSato et al, 2005), so the possibility of an indirect effect exists. These findings are in harmony with previous findings, when young Taihe hens were implanted with capsules releasing GnRH, plasma estradiol concentration was higher in the GnRH group than in the control group, and it was concluded that GnRH capsouls stimulated sexual precocity and ovulation in young Taihe hens (Wang et al, 1996) .…”

Section: Gonadotrophins (Lh and Fsh)mentioning

confidence: 99%

GnRH ANALOGUE (BUSERELIN ACETATE) MODULATES REPRODUCTIVE PERFORMANCE IN „OLD HENS‟

2010

Egyptian Journal of Animal Production

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To test the influence of a GnRH analogue (buserelin acetate, BA) on the reproductive activity of aging hens, a total of sixty, 50-wk-old Alexandrian hens were randomly and equally distributed among three treatment groups. Two groups received weekly intramuscular injections of 0.1 or 0.2 mL of the GnRH analogue solution, providing 0.42 and 0.84 µg of buserelin acetate, respectively, for 1 month. The control group received 0.15 mL of physiological saline. Reproductive parameters (egg production, egg weight and egg mass) and plasma FSH, LH and Estradiol (E 2 ) were measured. Overall, respectively, resulted in 58% and 30% increases in LH concentrations; 77% and 50% increases in FSH concentrations; and 41% and 8% increases in E 2 concentrations; compared to control. Weekly egg production increased by 37% and 29% with low-and high-BA, respectively. Egg weight on the other hand responded differently to treatments, as it declined to 97% of control. It can be concluded that in Alexandrian laying hens the decrease in egg production associated with advancing age can be attributed to reduction in plasma LH; hence treating aging hens with the GnRH analogue was capable of increasing egg production.

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LHRH antagonist decreases LH and progesterone secretion but does not alter length of estrous cycle in heifers.

Cited by 7 publications

References 15 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

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

GnRH ANALOGUE (BUSERELIN ACETATE) MODULATES REPRODUCTIVE PERFORMANCE IN „OLD HENS‟

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