Effects of an LHRH antagonist on the time of occurrence and amplitude of the preovulatory LH surge, progesterone and estradiol secretion, and ovulation in superovulated Holstein heifers

Madill, Scott; Rieger, D.; Johnson, Walter H.; Walton, J.S.; Coy, David H.; Rawlings, N.C.

doi:10.1016/0093-691x(94)90510-p

Cited by 15 publications

(8 citation statements)

References 18 publications

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“…Besides of numerous human studies, Antarelix is an effective antiovulatory agent in rats and has been shown to suppress LH levels in the castrated ram (Deghenghi et al, 1993), in female sheep (Oussaid et al, 1999) and in pigs (Driancourt et al, 1995;Quesnel et al, 2000;Brüssow et al, 2001). At present, there is a limited number of reports on the effects of GnRH antagonists on reproductive function in cattle (Madill et al, 1994;Manikkam and Rajamahendran, 1994;Fike et al, 1997;Oussaid et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…The pituitary, however, maintains its ability to respond to a GnRH stimulus (Ludwig et al, 2000;Roth et al, 2000). The number of experimental studies on the effects of GnRH antagonists in cattle has been limited (Madill et al, 1994;Manikkam and Rajamahendran, 1994;Fike et al, 1997;Oussaid et al, 2000). The objective for this study was therefore to describe the gonadotropin-releasing effects of a GnRH antagonist treatment during the periovulatory period of heifers and compare it with the effects of an agonist treatment.…”

Section: Introductionmentioning

confidence: 99%

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Gonadotropin release in periovulatory heifers after GnRH analogs measured by two types of immunoassays

Schneider¹,

Bellmann²,

Becker³

et al. 2002

Exp Clin Endocrinol Diabetes

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This study on heifers (n = 27) compared the effects of a GnRH antagonist (Antarelix) and those of an agonist (Triptorelin) on gonadotropin release during the periovulatory period of the oestrous cycle. In three experiments (EXP I-III), an initial injection of GnRH analogs was given 48 h after a single PGF 2alpha pretreatment during the luteal phase, with a further five at 12 h intervals. A challenge by a GnRH agonist (Gonavet) was performed six hours after the last application of analogs. In EXP I (n = 9), heifers received six times 1.5 mg of Antarelix, 0.5 mg of Triptorelin, and mannitol (5%; control), respectively. In EXP II (n = 12), identical Antarelix and Triptorelin treatments were followed by a single injection of estradiol-17beta valerate (6 h after Gonavet). The dosage of Antarelix was increased to 5 mg for each injection in EXP III (n = 6). Measurement of LH in blood plasma frequently sampled was performed parallely by a competitive RIA method (EXP I + II) and by a sandwich-type electro-chemiluminescence-immunoassay (ECLIA) in EXP III. This non-isotopic technique was also used to additionally analyse FSH levels. Results of EXP I showed that the GnRH antagonist equally suppressed LH surges and ovulation. On the contrary, prior to suppression of LH levels due to down-regulation of pituitary GnRH receptors the agonist Triptorelin induced an initial increase in LH concentration which was followed by ovulation. In the control animals we observed endogenous LH surges as well as smaller elevations after the agonist (Gonavet) challenge. An increase was also observed in antagonist, but not in Triptorelin treated heifers. Pituitary GnRH receptors were not detectable in animals previously treated by the analogs, whereas concentrations between 2.2-21.0 fmol/mg protein were measured in controls. Results of EXP II confirmed the described effects of GnRH analogs. Additionally, it was shown that exogenous estradiol is able to release LH from the pituitary, although a previous treatment by a GnRH agonist had dropped the pulsatile gonadotropin secretion. Contrary to the LH pattern and despite elevated amounts of the antagonist, the mean concentration and pulse number of FSH were not influenced by the antagonist treatment (EXP III). These data confirmed that (a) the reversibly blocked pituitary function induced by a potent GnRH antagonist may be a useful tool to study gonadotropin-dependent final follicular growth as well as ovulation in cyclic heifers and (b) the novel non-isotopic ECLIA methods for the determination of FSH and LH provided practical alternatives to other immunoassay types.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gonadotropin release in periovulatory heifers after GnRH analogs measured by two types of immunoassays

Schneider¹,

Bellmann²,

Becker³

et al. 2002

Exp Clin Endocrinol Diabetes

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“…kg -1 of Antarelix [15] or Cetrorelix [14], the terminal half-life is longer for Antarelix (23 h) than for Cetrorelix (10 h). But these results must be used 261 cases, when antagonists have a delaying effect of 1 to 3 days on the LH surge and ovulation, this surge often attenuated, is observed after the end of the treatment [24]. In the present experiment the LH peaks seem rather low but are in the normal range of the control mares.…”

Section: Discussionmentioning

confidence: 54%

“…GnRH antagonists can be used to delay and synchronise the LH surge and ovulation in different species: heifers [24], gilts [29], goats [2], ewes [8] and in ovarian stimulation cycles for IVF in humans namely to prevent premature LH surge [1]. These antagonists are also of interest for studying requirements in gonadotrophin support for terminal follicular growth [6].…”

Section: Introductionmentioning

confidence: 99%

Comparison of the effects of two GnRH antagonists on LH and FSH secretion, follicular growth and ovulation in the mare

2002

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-The effects of two GnRH antagonists were tested in order to delay and/or synchronise ovulation in mares. Five mares received Antarelix (0.01 mg . kg -1 ), 5 mares received Cetrorelix (the same dose), 5 mares (control mares) received the vehicle intravenously, twice daily, for 8 days from the day the largest follicle reached 22 mm following prostaglandin administration. Ovulation was postponed in all mares injected with Antarelix (19.4 ± 1.2 days after the beginning of the treatment) and in 2/5 mares injected with Cetrorelix (20 ± 1 days) vs. 6.2 ± 0.4 days in control mares. During the treatment, LH concentrations were strongly depressed in Antarelix and in Cetrorelix mares (1.6 ± 0.1 and 3.8 ± 0.5 ng . mL -1 respectively vs. 21 ± 2.5 ng . mL -1 in control mares). In the 3 Cetrorelix mares which ovulated during the treatment, 2 initiated their LH surge at this moment. FSH concentrations were not affected in Antarelix or in Cetrorelix mares during the treatment (11.4 ± 1.3 and 7.9 ± 0.8 ng . mL -1 respectively vs. 10.5 ± 0.8 ng . mL -1 in control mares). In conclusion, Antarelix seems more efficient than Cetrorelix for postponing ovulation in mares. The role of LH in antral follicular development before the preovulatory stage is confirmed. Reprod. Nutr. Dev. 42 (2002) [251][252][253][254][255][256][257][258][259][260][261][262][263][264] 251 mare / GnRH antagonist / ovulation / FSH / LH

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“…When superovulated heifers were given a GnRH antagonist to delay the LH surge, number of transferable embryos was decreased (Madill et al, 1994).…”

Section: Lhmentioning

confidence: 99%

Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Wurst¹

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Ewes are polyestrous and litter-bearing seasonal breeders. Although average ovulation rates are sufficient, many ovulations do not result in live offspring and ewes normally breed only once per year. As ovulation rate increases, so does the number of ovulations not represented by live births. When ultrasonographic analysis is limited to ovarian follicles that grow from 3 to 5 mm, follicular waves can be identified in sheep. In most cases, ovulatory follicle(s) develop from the ultimate follicular wave; however, ovulatory follicles can be derived from penultimate or earlier follicular waves. The relationship between lifespan of large follicles and fertility is controversial in sheep. In experiment 1, three approaches to create a model to compare fertility when ovulatory follicles developed from only the ultimate follicular wave or both ultimate and penultimate waves were tested. Ewes were treated on d 10 or 11 with 50 μg of GnRH i.m., the largest follicle(s) (≥ 4 mm) on each ovary were electrocauterized, or ewes were treated with 50 µg estradiol benzoate and 50 mg progesterone or 100 µg estradiol benzoate and 50 mg progesterone in attempts to induce follicular regression or luteinization. Corpora lutea were counted by ultrasound 7 days following estrus in order to verify ovulation of follicles that disappeared post estrus. Pregnancy was determined and embryos were counted 20 to 30 days following estrus. Neither treatment with GnRH nor estradiol and progesterone consistently caused regression or luteinization of ovulatory-sized follicles. Follicular ablation was successful in increasing the proportion of ovulations originating from the ultimate follicular wave in Dorset/Suffolk cross ewes, but did not alter the proportions of ovulations fom different waves in Polypay ewes. Average age of the ovulatory follicle was affected only in Dorset/Suffolk cross ewes. Due to lack of treatment effects, ovulatory follicles were evaluated regardless of treatment for effects on embryonic or fetal losses. Although loss tended to differ among follicular age combinations and wave sources of ovulatory follicles within ewes, older follicles did not have worse outcomes than younger follicles. Lactating ewes have not responded to treatments for the induction of estrus that are effective in dry ewes during the anestrous season. In experiment 2, lactating anestrous ewes 26 to 71 days postpartum were treated with either 25 or 50 mg progesterone/day for five days before ram introduction (RI). Twelve hours after RI, lambs were removed from half of the ewes in each group for 72 hours. Estrous response was recorded and ewes were scanned by transrectal ultrasonography on days 8 and 35 to 45 to determine ovulation rate, and pregnancy rate and number of embryos/fetuses, respectively. Number of lambs born was recorded at lambing. No effect of lamb removal was found for any variable examined. However, the lower dosage of progesterone reduced the mean time to estrus, increased the proportion of ewes ovulating, and decreased an incredible work ethic ...

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Effects of an LHRH antagonist on the time of occurrence and amplitude of the preovulatory LH surge, progesterone and estradiol secretion, and ovulation in superovulated Holstein heifers

Cited by 15 publications

References 18 publications

Gonadotropin release in periovulatory heifers after GnRH analogs measured by two types of immunoassays

Gonadotropin release in periovulatory heifers after GnRH analogs measured by two types of immunoassays

Comparison of the effects of two GnRH antagonists on LH and FSH secretion, follicular growth and ovulation in the mare

Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

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