Plasma LH and testosterone responses to gonadotrophin-releasing hormone in adult red deer (Cervus elaphus) stags during the annual antler cycle

1988 ◽  
Vol 117 (1) ◽  
pp. 35-41 ◽  
Author(s):  
P. F. Fennessy ◽  
J. M. Suttie ◽  
S. F. Crosbie ◽  
I. D. Corson ◽  
H. J. Elgar ◽  
...  
Keyword(s):  
Red Deer ◽  
Plasma Concentrations ◽  
Reproductive Hormones ◽  
Sexual Cycle ◽  
Late Winter ◽  
Releasing Hormone ◽  
Antler Growth ◽  
Velvet Antler ◽  
Antler Cycle ◽  
Gonadotrophin Releasing Hormone

ABSTRACT Eight adult red deer stags were given an i.v. injection of synthetic gonadotrophin-releasing hormone (GnRH) on seven occasions at various stages of the antler cycle, namely hard antler in late winter, casting, mid-velvet growth, full velvet growth, antler cleaning and hard antler both during the rut and in mid-winter. The stags were allocated at random on each occasion to one of four doses, i.e. 1, 3, 10 or 95 μg GnRH. Blood samples were taken before GnRH injection and for up to 2 h after injection. Pituitary and testicular responses were recorded in terms of plasma LH and testosterone concentrations. There was an increase in plasma concentration of LH after the GnRH injection in all stags at all stages of the antler cycle. Dose-dependent responses of LH to GnRH in terms of area under the curve were apparent at all stages of the antler cycle. The lowest responses were recorded at casting, during velvet antler growth and at the rut sampling. The pattern of testosterone response reflected the inter-relationship of the antler and sexual cycles with very low testosterone responses occurring at casting and during velvet antler growth. The responses were higher at antler cleaning and then increased to a maximum at the rut before declining to reach their nadir at casting. The results are consistent with a hypothesis that the antler cycle, as a male secondary sexual characteristic, is closely linked to the sexual cycle and its timing is controlled by reproductive hormones. Low plasma concentrations of testosterone, even after LH stimulation, are consistent with the hypothesis that testosterone is unnecessary as an antler growth stimulant during growth. J. Endocr. (1988) 117, 35–41

Temporal changes in LH and testosterone and their relationship with the first antler in red deer (Cervus elaphus) stags from 3 to 15 months of age

1991 ◽  
Vol 131 (3) ◽  
pp. 467-474 ◽  
Author(s):  
J. M. Suttie ◽  
P. F. Fennessy ◽  
S. F. Crosbie ◽  
I. D. Corson ◽  
F. J. Laas ◽  
...  
Keyword(s):  
Body Weight ◽  
Cervus Elaphus ◽  
Red Deer ◽  
Plasma Concentrations ◽  
Pulse Frequency ◽  
Growth Stages ◽  
Second Phase ◽  
Pulsatile Secretion ◽  
Antler Growth ◽  
Velvet Antler

ABSTRACT Blood samples were taken from six tame red deer stags at 3–15 months of age once a month from a jugular catheter every 30 min for 24 h to investigate hormonal secretion during puberty and during growth of the pedicle and first antler. All plasma samples were analysed for LH and testosterone concentrations and the resultant data were analysed using the PULSAR pulse detection routine. In addition each stag was injected with gonadotrophin-releasing hormone (GnRH; 20 ng/kg body weight) after the above samples had been taken and the bleeding regimen was continued for a further 2 h. Body weight, antler size and status (i.e. whether the stags had a pedicle or antler) were also recorded. The pulsatile secretion of LH could be considered to have occurred in three phases. The first of these was one of development, with the LH pulse frequency increasing to 8 pulses/24 h, the second a phase of regression, with a decrease in LH pulse frequency to 2 pulses/24 h, and finally a second phase of development characterized by increased LH pulse frequency to 12 pulses/24 h. Testosterone secretion generally followed the same pattern. During the period before the permanent bony pedicles grew, there were less than five LH pulses/24 h. When the pedicles were growing, LH and testosterone pulsatile secretion increased but the pulse frequency of both hormones fell during velvet antler growth. However, the overall mean testosterone level did not significantly decrease between the growth stages (2·74 and 2·29 nmol/l respectively) although mean testosterone plasma rose during pedicle growth and fell during velvet antler growth. Both hormone plasma concentrations increased dramatically, and testosterone was particularly high (11·82 nmol/l), at the time of antler cleaning. All stags responded to exogenous GnRH by secreting LH and testosterone in all sampling periods. The LH response to GnRH increased during pedicle growth and fell during antler growth before rising again in autumn as the breeding season approached. Testosterone responses largely paralleled those of LH except that they remained high in early antler development. The results are consistent with the following hypotheses. (1) Pedicle initiation is caused by increased plasma level of testosterone stimulated by increasing LH pulse frequency and (2) testosterone is stimulatory for pedicle growth but not necessarily so for velvet antler growth. Journal of Endocrinology (1991) 131, 467–474

Effects of immunization against GnRH upon body growth, voluntary food intake and plasma hormone concentration in yearling red deer stags (Cervus elaphus)

1993 ◽  
Vol 121 (3) ◽  
pp. 381-388 ◽  
Author(s):  
D. O. Freudenberger ◽  
P. R. Wilson ◽  
T. N. Barry ◽  
Y. X. Sun ◽  
R. W. Purchas ◽  
...  
Keyword(s):  
Cervus Elaphus ◽  
Red Deer ◽  
Plasma Concentrations ◽  
Late Summer ◽  
Early Summer ◽  
Body Growth ◽  
Scrotal Circumference ◽  
Voluntary Feed Intake ◽  
Antler Growth ◽  
Velvet Antler

SUMMARYRed deer stags in New Zealand were given a series of immunizations against GnRH at 9–12 months of age (spring/early summer) in 1989 and 1990 and the effects upon plasma concentrations of luteinizing hormone (LH) and testosterone during the rut (15–17 months; autumn) and upon body growth to slaughter at 22 months (spring) were studied in two experiments. Control animals showed a sharp peak in plasma LH and testosterone concentration during late summer/early autumn, just preceding the rut, with scrotal circumference increasing to a maximum during the rut; body growth stopped during the rut in Expt 1 but not in Expt 2. Immunization caused the development of significant antibodies against GnRH during late spring and summer, and reduced but did not eliminate the increase in plasma LH and testosterone and scrotal enlargement leading up to the rut. Immunization did not affect body growth or voluntary feed intake during the rut in either experiment, but in Expt 1 early immunization significantly increased growth during both the pre-rut and post-rut periods. Immunization did not effect dressing out percentage, slightly increased carcass fatness in Expt 1 but not Expt 2, and reduced velvet antler growth by 12 months of age.

Anti-fertility effects of oral medroxyprogesterone acetate in rabbits

1996 ◽  
Vol 8 (8) ◽  
pp. 1185 ◽  
Author(s):  
NO Oguge ◽  
GK Barrell
Keyword(s):  
Single Dose ◽  
Luteinizing Hormone ◽  
Medroxyprogesterone Acetate ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Multiple Dosing ◽  
Releasing Hormone ◽  
Single Meal ◽  
Gonadotrophin Releasing Hormone ◽  
Hypothalamic Level

Studies on the anti-fertility effects of medroxyprogesterone acetate (MPA) were conducted in rabbits. The bioavailability of MPA and plasma concentrations of progesterone and luteinizing hormone (LH) after mating were monitored following a single meal containing MPA (1000 mg) in entire does (n = 4); the response to gonadotrophin-releasing hormone (GnRH; 250 ng) was also observed in MPA-treated, ovariectomized does (n = 6). The reproductive tracts of rabbits mated following MPA treatment were examined 28-30 h after mating. Another group of rabbits (n = 4) received a single dose of MPA on Days 1, 10 or 19 after mating or daily for five days from Day 24. After dosage with 1000 mg MPA, plasma concentrations of MPA were detectable for eight days. However, following multiple dosing (10 mg, 5 days) MPA was detectable in the plasma for two days. MPA reduced the rate of ovulation and suppressed the increase in plasma concentrations of progesterone and LH observed after mating for four days, but had no effect on the response to GnRH. When administered late in gestation, MPA caused the death of fetuses. These results demonstrate an inhibitory effect of MPA on ovulation, probably at the hypothalamic level, and impairment of gestation or parturition.

Effects of pituitary-gonadal suppression with a gonadotrophin-releasing hormone agonist on fetal gonadotrophin secretion, fetal gonadal development and maternal steroid secretion in the sheep

1994 ◽  
Vol 141 (2) ◽  
pp. 317-324 ◽  
Author(s):  
G B Thomas ◽  
A S McNeilly ◽  
F Gibson ◽  
A N Brooks
Keyword(s):  
Gnrh Agonist ◽  
Fetal Development ◽  
Plasma Concentrations ◽  
Gonadal Development ◽  
Maternal Circulation ◽  
Biodegradable Implant ◽  
Steroid Secretion ◽  
Releasing Hormone ◽  
Pituitary Glands ◽  
Gonadotrophin Releasing Hormone

Abstract In order to investigate the regulation of the hypothalamo-pituitary-gonadal axis during fetal development, sheep fetuses at day 70 of gestation were implanted subcutaneously with a biodegradable implant containing the longacting gonadotrophin-releasing hormone (GnRH) agonist, buserelin. The treatment of fetuses with a GnRH agonist throughout the last half of gestation (term=145 days) abolished the increase in plasma LH concentrations that was seen in 2-day-old control lambs in response to an injection of GnRH. This attenuated response was associated with corresponding reductions in the pituitary content of LH and FSH. Immunolocalization studies revealed that pituitary glands from newborn lambs implanted with a GnRH agonist during fetal development were devoid of immunopositive LH- and FSH-containing cells. At birth the testicular weights of GnRH agonist-treated ram lambs were significantly decreased by 40% when compared with controls. This was associated with a 45% reduction in the total number of Sertoli cells per testis. In newborn ewe lambs GnRH agonist treatment had no effect on ovarian weight or on the morphological appearance of the ovaries. GnRH agonist treatment had no effect on the plasma concentrations of progesterone and oestrone in the maternal circulation or on the length of gestation. These results show (1) that GnRH positively regulates the synthesis and secretion of gonadotrophins in the fetus, (2) that reduced fetal gonadotrophic support during the last half of gestation results in a reduction in testicular growth, and (3) that fetal gonadotrophins do not affect maternal steroid secretion. Journal of Endocrinology (1994) 141, 317–324

Use of a new drug delivery formulation of the gonadotrophin-releasing hormone analogue Deslorelin for reversible long-term contraception in male dogs

2003 ◽  
Vol 15 (6) ◽  
pp. 317 ◽  
Author(s):  
A. Junaidi ◽  
P. E. Williamson ◽  
J. M. Cummins ◽  
G. B. Martin ◽  
M. A. Blackberry ◽  
...  
Keyword(s):  
Slow Release ◽  
Semen Quality ◽  
Animal Health ◽  
Plasma Concentrations ◽  
Testicular Volume ◽  
Releasing Hormone ◽  
Detectable Range ◽  
Effect Of Treatment ◽  
Gonadotrophin Releasing Hormone

In the present study, we tested the effect of treatment with a slow-release implant containing the gonadotrophin-releasing hormone agonist DeslorelinTM (Peptech Animal Health Australia, North Ryde, NSW, Australia) on pituitary and testicular function in mature male dogs. Four dogs were treated with Deslorelin (6-mg implant) and four were used as controls (blank implant). In control dogs, there were no significant changes over the 12 months of the study in plasma concentrations of luteinising hormone (LH) or testosterone, or in testicular volume, semen output or semen quality. In Deslorelin-treated dogs, plasma concentrations of LH and testosterone were undetectable after 21 and 27 days, testicular volume fell to 35% of pretreatment values after 14 weeks and no ejaculates could be obtained after 6 weeks. Concentrations returned to the detectable range for testosterone after 44 weeks and for LH after 51 weeks and both were within the normal range after 52 weeks. Semen characteristics had recovered completely by 60 weeks after implantation. At this time, the testes and prostate glands were similar histologically to those of control dogs. We conclude that a single slow-release implant containing 6 mg Deslorelin has potential as a long-term, reversible antifertility agent for male dogs.

Evaluating velvet antler growth in red deer stags (Cervus elaphus) using hand-held and digital infrared thermography

2010 ◽  
Vol 90 (1) ◽  
pp. 13-21 ◽  
Author(s):  
S Bowers ◽  
S Gandy ◽  
T Dickerson ◽  
C Brown ◽  
T Strauch ◽  
...  
Keyword(s):  
Cervus Elaphus ◽  
Growth Rates ◽  
Red Deer ◽  
Growth Period ◽  
Early Growth ◽  
Main Beam ◽  
Antler Growth ◽  
Velvet Antler ◽  
Late Growth ◽  
Over Time

The objectives of this study were to evaluate whether velvet antler (VA) surface temperature gradients, as measured by either a single-spot infrared temperature (SST) sensor (SSTS; exp. 1) or digital infrared temperature (DIT) imaging (DITI; exp. 2), would pattern VA growth. In exp. 1, growth rates and SST were obtained from yearling (n = 8) and mature (n = 17) red deer stags (Cervus elaphus) every 14 d following eruption through day 56 in yearlings and day 112 in mature stags. In exp. 2, growth rates and DIT (main beam VA base, mid and tip temperatures) were obtained from red deer stags (n = 31) every 14 d following eruption through day 126. Background temperatures were recorded in conjunction with thermal antler measurements. In exp. 1, yearling VA base and tip SST were positively correlated with one another (P < 0.01); however, both measurements were also positively correlated with background SST (P < 0.05). In mature stags, VA base SST paralleled (P < 0.05) background SST measures, while tip SST did not change from day 56 through day 112. In exp. 2, VA DIT changed (P < 0.01) over time and differed (P < 0.01) between base, mid and tip. During the early growth period, VA temperatures increased (P < 0.05) from 38.9 ± 0.2°C at the base to 39.3 ± 0.2°C at the tip of the antler. In contrast, during the late growth period, DIT was higher (P < 0.01) at the base (36.8 ± 0.3°C) than at the tip (35.7 ± 0.3°C) of the antler. In conclusion, SSTS did not have the sensitivity to signify changes in antler growth rates. However, in exp. 2 using DITI, VA thermogenesis paralleled VA growth suggesting that DITI may have value in monitoring VA growth. Key words: Velvet antler, red deer, thermography

Pituitary and testicular endocrine responses to exogenous gonadotrophin-releasing hormone (GnRH) and luteinising hormone in male dogs treated with GnRH agonist implants

2007 ◽  
Vol 19 (8) ◽  
pp. 891 ◽  
Author(s):  
A. Junaidi ◽  
P. E. Williamson ◽  
G. B. Martin ◽  
P. G. Stanton ◽  
M. A. Blackberry ◽  
...  
Keyword(s):  
Leydig Cells ◽  
Luteinising Hormone ◽  
Plasma Concentrations ◽  
Control Group ◽  
Release Formulation ◽  
Male Adult ◽  
Releasing Hormone ◽  
Slow Release Formulation ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Releasing Hormone

The present study tested whether exogenous gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH) can stimulate LH and testosterone secretion in dogs chronically treated with a GnRH superagonist. Twenty male adult dogs were assigned to a completely randomised design comprising five groups of four animals. Each dog in the control group received a blank implant (placebo) and each dog in the other four groups received a 6-mg implant containing a slow-release formulation of deslorelin (d-Trp6-Pro9-des-Gly10–LH-releasing hormone ethylamide). The same four control dogs were used for all hormonal challenges, whereas a different deslorelin-implanted group was used for each challenge. Native GnRH (5 μg kg–1 bodyweight, i.v.) was injected on Days 15, 25, 40 and 100 after implantation, whereas bovine LH (0.5 μg kg–1 bodyweight, i.v.) was injected on Days 16, 26, 41 and 101. On all occasions after Day 25–26 postimplantation, exogenous GnRH and LH elicited higher plasma concentrations of LH and testosterone in control than deslorelin-treated animals (P < 0.05). It was concluded that, in male dogs, implantation of a GnRH superagonist desensitised the pituitary gonadotrophs to GnRH and also led to a desensitisation of the Leydig cells to LH. This explains, at least in part, the profound reduction in the production of androgen and spermatozoa in deslorelin-treated male dogs.

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