Effect of chronic treatment with the gonadotrophin-releasing hormone agonist azagly-nafarelin on basal concentrations of LH in prepubertal bulls (original) (raw)
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Journal of andrology
The objective of this study was to determine if prolonged pulsatile administration of homologous gonadotropin-releasing hormone (GnRH) at therapeutic or 5x therapeutic doses would cause down-regulation of the stallion's hypothalamic-pituitary-testicular axis. Fifteen stallions were randomly assigned to three treatment groups (n=5/group) and received a 0.5 ml subcutaneous dose of saline (group 1), 50 microg GnRH (group 2), or 250 microg GnRH (group 3) every 2 hours for 75 days. Weekly evaluations of follicle stimulating hormone, luteinizing hormone, and testosterone and monthly evaluations of daily sperm output and spermatozoal motility failed to demonstrate any decreased pituitary or gonadal responsiveness within or among treatment groups (P > 0.1) as a result of treatment with GnRH. Results of this study demonstrate that the hypothalamic-pituitary-testicularaxis of the stallion, unlike that of other domestic species, is remarkably refractory to GnRH-induced down-regulation.
Journal of Reproduction and Development, 2011
The present study investigated the basal levels and GnRH-induced responses of peripheral testosterone and estrogen in Holstein bulls with poor semen quality. On the basis of semen parameters, bulls (n=5) having poor semen quality were selected as experimental bulls, and good semen quality bulls (n=4) were used as control bulls. Both groups were treated intramuscularly once with GnRH (250 μg of fertirelin acetate). Blood samples were collected at-1 day (d),-30 min and 0 h (treatment) followed by every 30 min for 5 h and 1, 3 and 5 d post-GnRH treatment (PGT), and LH, testosterone and estradiol-17β (E2) concentrations were measured. The pretreatment concentrations were used as basal levels. The percentage increments based on the 0-h levels were calculated per bull for each sampling time until 5 h PGT, and differences were compared between the experimental and control groups. The PGT concentrations of testosterone and basal and PGT concentrations of E2 were significantly lower in the experimental group. The testosterone increment in the experimental group was delayed and significantly lower from 1 to 5 h PGT than those in the control group. It can be suggested that bulls with poor semen quality have delayed and lower GnRH-induced testosterone response and may also have lower estrogen levels.
EFFECT OF GnRH ANALOGUE ON LIBIDO AND SEMEN CHARACTERISTICS OF PUBERAL BUFFALO BULLS
Egyptian puberal buffalo bulls (n=9); aged 15-18 months; allocated into three groups (n= 3/group) to verify the effect of different doses (8 μg, 12 μg or 16 μg) of GnRH analogue (Buserelin acetate) on the sexual desire and semen characteristics. Bulls treated with 12 μg of Buserelin were superior to those injected with 8 µg or 16 µg where it shortened the reaction time (6.51±0.38min. vs. 7.48±0.41min. and 7.46±0.40min., respectively) and improved the semen quantity: increased the ejaculate volume (2.22± 0.13ml vs. 1.89± 0.13 ml and 1.54±0.11ml, respectively) and sperm cell concentration (957±86.60×106 sperm/ml vs. 928±86.76×106 sperm/ml and 779±53.62×10 6 sperm/ml, respectively), improved the sperm motility (57.13±1.36% vs. 63.29±1.55% and 56.11±1.51%, respectively) and sperm livability (66.80± 1.23% vs. 69.12± 1.45% and 67.85± 1.87%, respectively), and lower sperm abnormalities (5.08±0.33% vs. 11.30± 0.95% and 9.16±0.49%, respectively). Instead, Buserelin injection increased testosterone levels in a dose-dependent-manner (1.73±0.57ng/ml, 4.61±1.28ng/ml and 4.79±1.21 ng/ml in 8 μg, 12 μg and 16 μg groups, respectively).These results demonstrated that GnRH injection at a dose of 12 μg is optimal to maximize the libido and semen quality of pubertal buffalo bulls. KEY WORDS: Buffalo bulls, GnRH, Semen, Testosterone ( (B BV VM MJ J--S SE E [ [1 1] ]: : 2 28 8--3 34 4; ; 2 20 01 11 1) ) P BENHA UNIVERSITY FACULTY OF VETERINARY MEDICINE B BE EN NH HA A V VE ET TE ER RI IN NA AR RY Y M ME ED DI IC CA AL L J JO OU UR RN NA AL L B BE EN NH HA A V VE ET TE ER RI IN NA AR RY Y M ME ED DI IC CA AL L J JO OU UR RN NA AL L ( (2 20 01 11 1) )--S SP PE EC CI IA AL L
The present study aims to investigate the Luteinizing hormone (LH), testosterone and total estrogens response to exogenous gonadotropin-releasing hormone (GnRH) in adult crossbred bulls with differing semen quality. Fourteen adult crossbred bulls of differing semen quality were selected and treated with 10 mg of GnRH (Buserelin acetate) intramuscularly. Blood samples of the bulls were collected at an interval of 30 min commencing 1 h prior to GnRH treatment until 4 h post-GnRH treatment and thereafter, at an interval of 1 h for the next 3 h. The endocrine response in terms of peak values, area under the curve, and the time taken to attain peak values for LH, testosterone, and total estrogens were evaluated in all the bulls. The mean 7 SEM peak levels of LH, testosterone, and total estrogens were found to be 150 7 24.1, 5.3 7 0.69, and 0.077 0.01 ng/mL, respectively. The mean 7 SEM area under the curve of LH, testosterone, and total estrogens were found to be 392 7 51.3, 23.57 3.4, and 0.32 7 0.04 ng/mL Â h, respectively. The relationships between hormonal responses (LH, testosterone, and total estrogens) and semen quality were analyzed using the linear regression method, which provided nonsignificant (P 40.05) results. This study indicated that the gonadal and pituitary hormonal response to single exogenous GnRH treatment may have no relationship with the semen quality of crossbred bulls.
Research in Veterinary Science, 2015
GnRH treatment has been suggested to increase testosterone levels temporarily and to stimulate libido in stallions, but its use has not fully ascertained in dromedary camels. The aim of this work was to study the effects of administering 100 µg of GnRH on testosterone profile, libido and semen parameters in dromedary camels. The same bulls were used as self-controls and experimental group. Blood samples were collected every 20 minutes (T0-T12) for 4 hours, and semen collections were performed over a 2-hour period after T12. GnRH was administered immediately after T0. In GnRH-treated bulls, testosterone levels showed an upward trend, peaking after 140 minutes, and then slowly decreasing. GnRH administration also led to a decrease in mating time and an increase in spermatozoa concentration. Overall, it seems that administration of 100 µg GnRH might increase testosterone levels temporarily and enhance camel reproduction performance.
Annales de Biologie Animale Biochimie Biophysique, 1979
The LH and testosterone release after a single injection (0.25 mg) of Gonadoliberin (LRH) were studied in a total of 23 bulls before and about puberty. Both LH and testosterone were measured by radioimmunoassay of jugular vein blood samples taken at frequent intervals. LRH caused release of LH at all ages but the magnitude of the LH increase in response to LRH was significantly higher at 3 and 5 months (mean total response 4.3 f J-g/ml x 150 min) than at older ages (3.1 pg/ml x 150 min.). By contrast the mean total response of testosterone to LRH increases from very low levels (0.07 fJ-g/ml x 150 min) at 3 months of age to about 0.65 !,g/ml x 150 min. between the ages of 7 and 13 months. The mean LH responses vary significantly among individuals and the intra-class correlation coefficient r is 0.3 (p < 0.02). These results provide evidence of two distinct periods prior to puberty with regard to LH and testosterone release in response to LRH : one before 7 months of age during which LH release is very sensitive to LRH and the testosterone low, and the other from 7 months until after puberty, when no more changes in the magnitude of the responses can be seen. However, the individual magnitude of the response during the second period does not seem to be independent of that seen in the former period. Introduction. A further understanding of pituitarytestes relationships in the young bull might be achieved by critical determination of pituitary gonadotropic and gonadal hormone concentrations at various ages prior to or around the time of puberty. Puberty, defined as the release of the first spermatozoa, occurs in this species at about the eigth or ninth month after birth (Ortavant et al., 1977). The reprints should be requested to : Laboratoire d'Hormonologie, UNCEIA, 13, rue Jouet, 94700 Maisons-Alfort, France.
Reproduction, Fertility and Development, 2007
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-Trp 6 -Pro 9 -des-Gly 10 -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.
Theriogenology, 1995
The investigation of the fertility capacity of A.I. bulls is one of the most important factors in their genetic improvement. The aim of this study was to examine the relationship between the results of the GnRH test and the measured and calculated size of the testicles and sperm parameters (sperm density and velocity, percentage of live and motile spermatozoa). Data was collected during three experiments from a total of 81 Holstein-Friesian breeding bulls at the National Artificial Insemination Centre of Hungary. In Experiment I. a very close correlation (r=0.64, p<O.OOl ; r=0.66, p<O.OOl ; r=0.99, p<O.OOl; r=0.75, pcO.001) was found between the size of testes (weight, volume, width, length) and the calculated volume. According to the data, we may calculate volume based on the width of testicles measured by sonography.
Journal of Animal Science, 2005
The objective was to compare testis characteristics of Zebu bulls treated with the GnRH agonist, deslorelin, at different times and for different durations during their development. An additional objective was to determine the usefulness of a stain for the transcription factor GATA-binding protein 4 (GATA-4) as a specific marker for Sertoli cell nuclei in cattle. Bulls (54) were allocated to nine groups (n = 6) and received s.c. deslorelin implants as follows: G1 = from birth to 3 mo of age; G2 = from 3 to 6 mo; G3 = from 6 to 9 mo; G4 = from 9 to 12 mo; G5 = from birth to 15 mo; G6 = from 3 to 15 mo; G7 = from 6 to 15 mo; G8 = from 12 to 15 mo; and G9 (control) = no implant. Bulls were castrated at 19 mo of age. Paraffin sections (10 m) were subjected to quantitative morphometry and GATA-4 immunohistochemistry. At castration, all bulls in the control group (6/6) had attained puberty (scrotal circumference ≥ 28 cm), whereas a smaller proportion (P < 0.05) had reached puberty in G2 (2/5) and G6 (1/ 6). Bulls in G2 and G6 also had a lesser (P < 0.05) testis