Corpus luteum life span and pituitary oestrogen and progesterone receptors in cyclic and gonadotrophin-releasing hormone-treated anoestrous ewes

2005 ◽  
Vol 17 (7) ◽  
pp. 721 ◽  
Author(s):  
C. Tasende ◽  
M. Rodríguez-Piñón ◽  
S. Acuña ◽  
E. G. Garófalo ◽  
M. Forsberg
Keyword(s):  
Luteal Phase ◽  
Luteinising Hormone ◽  
Binding Assay ◽  
Hormone Secretion ◽  
Progesterone Receptors ◽  
Oestrous Cycle ◽  
Inhibitory Effects ◽  
Releasing Hormone ◽  
Expected Time ◽  
Gonadotrophin Releasing Hormone

The present study investigated the pituitary oestrogen (ER) and progesterone (PR) receptor concentrations in ewes during the oestrous cycle in the breeding season (n = 19), and in anoestrous ewes treated with gonadotrophin-releasing hormone (GnRH) (n = 11) and anoestrous ewes treated with progesterone + GnRH (n = 11). The pituitary ER and PR concentrations at the expected time of ovulation and in the early and late luteal phases were measured by binding assay. The pattern of pituitary ER and PR concentrations in the progesterone + GnRH-treated ewes resembled the pattern found during the normal oestrous cycle, with ER and PR concentrations decreasing from the time of ovulation to the early luteal phase. In contrast, in ewes treated with GnRH alone, ER and PR concentrations increased in the early luteal phase, which may increase the inhibitory effects of steroid hormones on luteinising hormone secretion, ultimately leading to the development of subnormal luteal phases.

The effect of a potent gonadotrophin-releasing hormone antagonist on ovarian secretion of oestradiol, inhibin and androstenedione and the concentration of LH and FSH during the follicular phase of the sheep oestrous cycle

1990 ◽  
Vol 126 (3) ◽  
pp. 377-384 ◽  
Author(s):  
B. K. Campbell ◽  
A. S. McNeilly ◽  
H. M. Picton ◽  
D. T. Baird
Keyword(s):  
Gnrh Antagonist ◽  
Venous Blood ◽  
Hormone Secretion ◽  
Experimental Period ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Blood Samples ◽  
Releasing Hormone ◽  
Inhibitory Feedback ◽  
Gonadotrophin Releasing Hormone

ABSTRACT By selective removal and replacement of LH stimulation we sought to examine the relative importance of inhibin and oestradiol in controlling FSH secretion, and the role of LH in the control of ovarian hormone secretion, during the follicular phase of the oestrous cycle. Eight Finn–Merino ewes which had one ovary removed and the other autotransplanted to a site in the neck were given two injections of a gonadotrophin-releasing hormone (GnRH) antagonist (50 μg/kg s.c.) in the follicular phase of the cycle 27 h and 51 h after luteal regression had been induced by cloprostenol (100 μg i.m.). Four of the ewes received, in addition, i.v. injections of 2·5 μg LH at hourly intervals for 23 h from 42 to 65 h after GnRH antagonist treatment. Ovarian jugular venous blood samples were taken at 10-min intervals for 3 h before and 5 h after the injection of antagonist (24–32 h after cloprostenol) and from 49 to 53 h after antagonist (74–78 h after cloprostenol). Additional blood samples were taken at 4-h intervals between the periods of intensive blood sampling. The GnRH antagonist completely inhibited endogenous pulsatile LH secretion within 1 h of injection. This resulted in a marked decrease in the ovarian secretion of oestradiol and androstenedione (P<0·001), an effect that was reversible by injection of exogenous pulses of LH (P<0·001). The pattern of ovarian inhibin secretion was episodic, but removal or replacement of stimulation by LH had no effect on the pattern or level of inhibin secretion. Peripheral concentrations of FSH rose (P<0·01) within 20 h of administration of the antagonist and these increased levels were maintained in ewes given no exogenous LH. In ewes given LH, however, FSH levels declined within 4 h of the first LH injection and by the end of the experimental period the levels of FSH were similar to those before administration of antagonist (P<0·01). These results confirm that ovarian oestradiol and androstenedione secretion, but not inhibin secretion, is under the acute control of LH. We conclude that oestradiol, and not inhibin, is the major component of the inhibitory feedback loop controlling the pattern of FSH secretion during the follicular phase of the oestrous cycle in ewes. Journal of Endocrinology (1990) 126, 377–384

Ovine serum and pituitary isoforms of luteinising hormone during the luteal phase

2006 ◽  
Vol 18 (4) ◽  
pp. 485 ◽  
Author(s):  
E. Arrieta ◽  
A. Porras ◽  
E. González-Padilla ◽  
C. Murcia ◽  
S. Rojas ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Relative Abundance ◽  
Luteal Phase ◽  
Luteinising Hormone ◽  
Saline Solution ◽  
Control Group ◽  
Acidic Ph ◽  
Releasing Hormone ◽  
Relative Composition ◽  
Gonadotrophin Releasing Hormone

The relative abundance of the different isoforms of pituitary and circulating luteinising hormone (LH) in ewes, at different times after the administration of gonadotrophin-releasing hormone (GnRH), during the luteal phase of the oestrous cycle was investigated. Sixteen ewes on Day 9 of their cycle were divided into four groups (n = 4). The control group (T0) received saline solution; the remaining animals received 100 μg GnRH (i.m.) 30, 90 or 180 min (T30, T90 and T180, respectively) before serum and pituitary gland collection. Luteinising hormone polymorphism was analysed by chromatofocusing (pH 10.5–3.5). The LH eluted from each chromatofocusing was grouped on the basis of the following three criteria: (1) according to the pH of elution (pH ≥ 10–3.5); (2) as either a basic (pH ≥ 7.5), neutral (pH 7.4–6.5) and acidic (pH ≤ 6.4) elution of LH of serum and hypophyseal origin; and (3) on the basis of distinct isoforms, of which 10 (A–J) were identifiable in hypophyseal extracts and four (A–D) were found in the serum. In general, the most abundant forms of LH in both the pituitary and serum, at all times, were basic. However, that proportion was greater in hypophyseal extracts (84 ± 3%, 81 ± 4%, 82 ± 3% and 83 ± 2% at T0, T30, T90 and T180, respectively) than in serum (51 ± 5%, 48 ± 10% and 54 ± 6% at T30, T90 and T180, respectively). Neutral and acidic LH made up a larger proportion of the total LH in sera (neutral: 17 ± 4%, 20 ± 6% and 23 ± 3% at T30, T90 and T180, respectively; acidic: 32 ± 8%, 32 ± 11% and 23 ± 6% at T30, T90 and T180, respectively) than in the pituitary extracts (neutral: 4.0 ± 0.7%, 10 ± 4%, 7 ± 2% and 5.0 ± 0.5% at T0, T30, T90 and T180, respectively; acidic: 12 ± 3%, 11 ± 2%, 12 ± 2% and 12 ± 2% at T0, T30, T90 and T180, respectively) at all times. These data reveal that the relative composition of the LH present in the pituitary gland and the LH secreted into the circulation is different, with more neutral and acidic isoforms being secreted. The pattern of circulating LH isoforms changes between 30 and 180 min after GnRH peak induction, with a greater proportion of isoform C (eluting between pH 7.0 and 6.5) at T180 compared with T30 and T90.

Effect of pulsatile infusion of gonadotrophin-releasing hormone on plasma oestradiol-17β concentrations and follicular development during naturally and artificially maintained high levels of plasma progesterone in heifers

1987 ◽  
Vol 112 (1) ◽  
pp. 77-85 ◽  
Author(s):  
R. G. Glencross
Keyword(s):  
Luteal Phase ◽  
Indirect Evidence ◽  
Follicular Development ◽  
Pulse Frequency ◽  
Oestrous Cycle ◽  
Plasma Progesterone ◽  
Releasing Hormone ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Plasma Oestradiol

ABSTRACT To stimulate a follicular-phase pattern of pulsatile LH release, gonadotrophin-releasing hormone (GnRH; 5 μg) was infused (i.v.) hourly into heifers for periods of 5–11 days during the luteal phase of the oestrous cycle, and also when plasma progesterone levels were increased artificially by means of a progesterone-releasing intravaginal device. Plasma oestradiol-17β concentrations increased from basal (EEE 2·5 pmol/l) to preovulatory peak levels (20–30 pmol/l) during the first 3 days of GnRH treatment. They were maintained at these values before returning to basal levels within 24 h of cessation of infusion. This response occurred regardless of the source of progesterone (endogenous or administered). Follicular development was observed by ovarian palpation (per rectum) in some heifers at the time of maximum secretion of oestradiol-17β. There was no detectable cervical mucus secretion or oestrous behaviour during these periods of high oestradiol-17β levels and ovulation did not occur. Treatment with GnRH did not affect plasma progesterone concentrations or oestrous cycle length. The study shows that oestradiol-17β secretion and follicular development (and the accompanying oestrus and ovulation) are suppressed during the luteal phase of the cycle by high concentrations of plasma progesterone, and provides strong indirect evidence that such inhibition is associated with a reduction in the pulse frequency of LH release. J. Endocr. (1987) 112, 77–85

Effect of a gonadotrophin-releasing hormone antagonist on luteinising hormone secretion and early pregnancy in gilts

2003 ◽  
Vol 15 (8) ◽  
pp. 451 ◽  
Author(s):  
J. V. Virolainen ◽  
R. J. Love ◽  
A. Tast ◽  
O. A. T. Peltoniemi
Keyword(s):  
Real Time ◽  
Early Pregnancy ◽  
Luteinising Hormone ◽  
Gnrh Antagonist ◽  
Hormone Secretion ◽  
Single Treatment ◽  
Short Term ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone

The aims of the present study were: (1) to determine the duration of suppression of luteinising hormone (LH) following a single treatment with a gonadotrophin-releasing hormone (GnRH) antagonist (BIM-21009; Biomeasure) at a dose of 100 μg kg−1; (2) to block LH pulses only for certain days of pregnancy; and (3) to determine the period of early pregnancy most susceptible to suppression of LH. Three groups of gilts were injected with 100 μg kg−1 on Day 16 (n = 5), 14 (n = 6) or 19 (n = 4) of pregnancy. Blood for LH analysis was collected at 20-min intervals for 12 h on the day before treatment and during varying stages of early pregnancy. Blood for progesterone analysis was collected daily and development of pregnancy was followed using real-time ultrasound. Prior to treatment, gilts had 2.6 ± 0.7 LH pulses per 12 h. The GnRH antagonist abolished LH pulses for a period of 2.7 ± 1.8 days and, thereafter, suppressed the resumed LH pulses (P < 0.05). Pregnancy was disrupted in three pigs (20%) with a mean treatment-to-abortion period of 4.7 days concurrent with a mean treatment-to-progesterone decline interval of 4.3 days. In a proportion of pigs, short-term LH suppression may cause early disruption of pregnancy.

Luteal stage dependence of pituitary response to gonadotrophin-releasing hormone in cyclic dairy ewes subjected to synchronisation of ovulation

2005 ◽  
Vol 17 (8) ◽  
pp. 769 ◽  
Author(s):  
G. S. Amiridis ◽  
I. Valasi ◽  
I. Menegatos ◽  
C. Rekkas ◽  
P. Goulas ◽  
...  
Keyword(s):  
Luteal Phase ◽  
Luteinising Hormone ◽  
Prostaglandin F2α ◽  
Causative Factor ◽  
Releasing Hormone ◽  
Treatment Groups ◽  
Dairy Ewes ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Additional Sample

Possible hormonal aberrations precluding conception or maintenance of pregnancy in dairy ewes subjected to ovulation synchronisation were investigated in this study. The pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was tested at different luteal stages in 36 ewes. Oestruses were synchronised by using progestagen-impregnated sponges and the animals were randomly allotted into one of three treatment groups (A, B and C; n = 12 for each). Treatments commenced on Days 4, 9 and 14 of the new cycle (oestrus was defined as Day 0). Ewes were given two GnRH injections, 5 days before and 36 h after a prostaglandin F2α (PGF2α) injection, and the animals were inseminated 12–14 h after the second GnRH injection (modified OVSYNCH). For luteinising hormone (LH) determination blood samples were withdrawn from six ewes of each group at the time of GnRH administration, and 30, 90, 180, 270 and 360 min later. Progesterone was assayed in samples taken every other day starting from oestrus and for 17 days after the second GnRH injection, and in an additional sample collected on the day of insemination. After the first GnRH injection, the LH concentration was higher in Group C than in Groups B and A (mean ± s.d.: 64.8 ± 10.0 ng mL−1, 41.3 ± 3.7 ng mL−1 and 24.6 ± 9.0 ng mL−1, respectively; P < 0.05), whereas after the second GnRH injection a uniform LH release was found in all groups. PGF2α caused a significant decrease in progesterone (P4) concentration in all groups; however, at artificial insemination ewes that conceived had significantly lower P4 concentration in comparison with those that failed to conceive. As early as Day 5, pregnant animals had higher P4 concentrations than non-pregnant animals. Overall, 21 animals conceived (seven, nine and five ewes from Groups A, B and C, respectively). These results indicate that the proposed protocol is equally effective in inducing a preovulatory LH surge at any stage of the luteal phase, and that elevated P4 concentration along with a delayed P4 increase should be considered as a causative factor for inability to conceive.

Modulation of Gonadotrophin-Releasing Hormone Secretion by an Endogenous Circadian Clock

2009 ◽  
Vol 21 (4) ◽  
pp. 339-345 ◽  
Author(s):  
P. E. Chappell ◽  
C. P. Goodall ◽  
K. J. Tonsfeldt ◽  
R. S. White ◽  
E. Bredeweg ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Hormone Secretion ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone

THE EFFECT OF CYPROTERONE ACETATE ON THE PLASMA GONADOTROPHIN RESPONSE TO GONADOTROPHIN RELEASING HORMONE

1976 ◽  
Vol 81 (3) ◽  
pp. 680-684 ◽  
Author(s):  
Richard A. Donald ◽  
Eric A. Espiner ◽  
R. John Cowles ◽  
Joy E. Fazackerley
Keyword(s):  
Testosterone Level ◽  
Cyproterone Acetate ◽  
Luteinising Hormone ◽  
Follicle Stimulating Hormone ◽  
Plasma Testosterone ◽  
Plasma Testosterone Level ◽  
Releasing Hormone ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Male Patients

ABSTRACT Cyproterone acetate (100–150 mg daily) was administered to 8 male patients with excessive libido. Within 3 months a significant fall (P < 0.02) in plasma testosterone was demonstrated. The plasma luteinising hormone (LH) and follicle stimulating hormone (FSH) responses to gonadotrophin releasing hormone (LH/FSH-RH) were also significantly impaired (P < 0.05). A direct correlation between the resting plasma testosterone level and the LH response to LH/FSH-RH was demonstrated (r = 0.743). It is concluded that the fall in plasma testosterone levels in patients receiving cyproterone acetate may be attributed to suppression of LH release, rather than an antiandrogen effect on the testis or hypothalamus.

Relationship between gonadotrophin subunit gene expression, gonadotrophin-releasing hormone receptor content and pituitary and plasma gonadotrophin concentrations during the rebound release of FSH after treatment of ewes with bovine follicular fluid during the luteal phase of the cycle

1992 ◽  
Vol 8 (2) ◽  
pp. 109-118 ◽  
Author(s):  
J. Brooks ◽  
W. J. Crow ◽  
J. R. McNeilly ◽  
A. S. McNeilly
Keyword(s):  
Follicular Fluid ◽  
Luteal Phase ◽  
Gnrh Receptor ◽  
Mrna Levels ◽  
Α Subunit ◽  
Luteal Regression ◽  
Releasing Hormone ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Secretion ◽  
Cessation Of Treatment

ABSTRACT The modulation of FSH secretion at the beginning and middle of the follicular phase of the cycle represents the key event in the growth and selection of the preovulatory follicle. However, the mechanisms that operate within the pituitary gland to control the increased release of FSH and its subsequent inhibition in vivo remain unclear. Treatment of ewes with bovine follicular fluid (bFF) during the luteal phase has been previously shown to suppress the plasma concentrations of FSH and, following cessation of treatment on day 11, a rebound release of FSH occurs on days 12 and 13. When luteal regression is induced on day 12, this hypersecretion of FSH results in an increase in follicle growth and ovulation rate. To investigate the mechanisms involved in the control of FSH secretion, ewes were treated with twice daily s.c. injections of 5 ml bFF on days 3–11 of the oestrous cycle and luteal regression was induced on day 12 with prostaglandin (PG). The treated ewes and their controls were then killed on day 11 (luteal), or 16 or 32h after PG and their pituitaries removed and halved. One half was analysed for gonadotrophin and gonadotrophin-releasing hormone (GnRH) receptor content. Total pituitary RNA was extracted from the other half and subjected to Northern analysis using probes for FSH-β, LH-β and common α subunit. Frequent blood samples were taken and assayed for gonadotrophins. FSH secretion was significantly (P<0.01) reduced during bFF treatment throughout the luteal phase and then significantly (P<0.01) increased after cessation of treatment, with maximum secretion being reached 18– 22h after PG, and then declining towards control values by 32h after PG. A similar pattern of LH secretion was seen after bFF treatment. Pituitary FSH content was significantly (P<0.05) reduced by bFF treatment at all stages of the cycle. No difference in the pituitary LH content was seen. The increase in GnRH receptor content after PG in the controls was delayed in the treated animals. Analysis of pituitary mRNA levels revealed that bFF treatment significantly (P<0.01) reduced FSH-β mRNA levels in the luteal phase. Increased levels of FSH-β, LH-β and α subunit mRNA were seen 16h after PG in the bFF-treated animals, at the time when FSH and LH secretion from the pituitary was near maximum. These results suggest that the rebound release of FSH after treatment with bFF (as a source of inhibin) is related to a rapid increase in FSH-β mRNA, supporting the concept that the rate of FSH release is directly related to the rate of synthesis.

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