首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 250 毫秒
1.
Eight mature light-breed stallions with normal testes size, sperm output and semen quality were used to evaluate response to 3 GnRH challenge regimens in the summer in southeast Texas. Gonadotropin releasing hormone (50 μg) was administered intravenously once to each of eight stallions after three days of sexual rest (50 μg GnRH-1X). The same stallions were administered either 5μg GnRH intravenously once hourly for three injections (5 μg GnRH-3X) and 15μg GnRH intravenously once (15μg GnRH-1X) one and two weeks later. Blood samples were collected prior to and at intervals after GnRH administration. Plasma was immediately separated from blood samples and was frozen until assayed for LH, FSH, estradiol and testosterone concentrations. Percentage changes in hormone concentrations from pre-treatment values (baseline) were analyzed by paired studient'st-test to detect significant rises in hormone concentrations. Group mean percentage changes in hormone concentrations were analyzed by analysis of variance to compare responses among treatments. A computerized peak-detection algorithm (PC Pulsar) was used to detect peaks in LH and testosterone concentrations following 5 μg GnRH-3X and 15 μg GnRH-1X treatment.No differences (P>0.10) were detected in percentage change from baseline concentration for LH, FSH, or testosterone at one or two hours after administration of any of the three regimens of GnRH. When more frequent sampling intervals were analyzed for 5 μg GnRH-3X or 15 μg GnRH-1X treatments, no differences were detected in percentage change from baseline concentration for any hormone at 15, 30 or 60 minutes. Thereafter, percentage changes in concentrations of LH and FSH remained increased for 5μg GnRH-3X compared to 15 μg GnRH-1X treated stallions (P<0.05). Percentage changes in concentrations of testosterone were increased for 5μg GnRH-3X compared to 15 μg GnRH-1X treated stallions from 180–300 min (P<0.05), while no differences (P>0.10) were detected between 5 μg GnRH-3X and 15 μg GnRH-1X treated stallions for changes in concentrations of estradiol throughout the experiment.For 15 μg GnRH-1X treated stallions, maximum concentrations of LH in PC Pulsar-detected peaks occurred most commonly at 15 to 30 minutes (7/8 treatment periods) after GnRH injection. Maximum concentrations of testosterone in PC Pulsar-detected peaks occurred most commonly at 60–120 min (7/8 treatment periods) after GnRH injection.A protocol of blood sampling prior to, and 15, 30, 60 and 120 minutes after, intravenous administration of small doses of GnRH would be practical for challenge testing of stallions during the breeding season. In order to reduce cost of hormone assays, we suggest assay of the pre-challenge blood sample (baseline) could include LH, FSH, testosterone and estradiol concentrations (to assess overall hypothalamic-pituitary-testicularfunction), while only LH and testosterone concentrations need be determined after GnRH administration (to assess pituitary and testicular responsiveness). Assay for LH could be done on only the 15 and 30 minute post-GnRH samples, and assay for testosterone could be done on only the 60 and 120 minute post-GnRH samples. Failure to achieve approximately a 50% increase in LH concentration by 30 minutes after GnRH administration, and/or failure to achieve approximately a 100% increase in testosterone concentration by two hours after GnRH administration, could be further pursued either by treatment with increasing dosages of GnRH, or repeated administration of GnRH at hourly intervals, as has been suggested by other workers.  相似文献   

2.
Effects of season and photoperiod on the anterior pituitary gland and testes were studied by responses to exogenous GnRH. Stallions were assigned to one of three treatments: 1) control, exposed to natural day length; 2) S-L, 8 h of light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984; or 3) S-S, 8:16 from July 16, 1982 until March 5, 1984. Approximately every 8 wk, stallions were administered GnRH (2 micrograms/kg BW) and blood was sampled at 20-min intervals for 2 h before and 8 h after GnRH administration. Concentrations of LH, FSH and testosterone were determined. Baseline concentrations (mean of pre-GnRH samples) of all hormones fluctuated seasonally (P less than .05), but only LH and testosterone displayed seasonal changes (P less than .05) in maximum response to GnRH (highest concentration above baseline after GnRH). The FSH response to GnRH was not affected (P greater than .05) by season, photoperiod or the season X treatment interaction. Exposure of S-L stallions to 16:8 in December resulted in early recrudescence of baseline concentrations of LH, FSH and testosterone. Maximum concentration of testosterone in response to GnRH was stimulated by 16:8, but the increase in baseline LH concentrations in S-L stallions was not associated with an increase in maximum LH response to GnRH. Seasonal patterns of baseline concentrations of FSH and testosterone and maximum LH response to GnRH in S-S stallions were similar to those for control stallions.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
Plasma concentrations of LH, FSH and testosterone are reported in stallions exhibiting a variety of reproductive problems. Stallions with poor libido were found to have low LH and FSH concentrations, while testosterone concentrations appeared normal. Stallions with good libido but experiencing ejaculatory disorders had normal concentrations of LH, FSH and testosterone. Older stallions experiencing a marked reduction in fertility had elevated FSH concentrations which were accompanied by increased LH concentrations in some cases, however, testosterone concentrations appeared normal in such stallions. Two young stallions which had experienced poor fertility (40 to 60% conception rates) from the beginning of their stud careers were found to have normal FSH and testosterone concentrations while LH concentrations were consistently low in one and normal in the other.  相似文献   

4.
The aim of the present study was to investigate the spermatogenic and Leydig cell activity in stallions with impaired semen quality after treatment with equine somatotropin. Experiments were performed using 18 adult clinically healthy stallions with poor semen quality which did not pass breeding soundness evaluation. The animals were randomly divided into a treatment (n = 9) and a control (n = 9) group. Over a period of 90 days, nine stallions received a daily intramuscular injection of 10 mg recombinant equine somatotropin (EquiGen, BresaGen Limited, Adelaide, Australia) and 9 control animals were injected with the same amount of physiological saline solution. During and until 2 months after treatment, semen characteristics and daily sperm output as well as plasma testosterone concentrations were determined monthly in all stallions. In addition, testosterone concentration measurement after stimulation with hCG was performed in all animals immediately before and at the end of the treatment period as well as 2 months later. Our results demonstrate that equine somatotropin (EquiGen) given daily in a dose of 10 mg per animal during 90 days had no significant effect neither on plasma testosterone concentrations and hCG-induced testosterone release nor on semen quality parameters in adult stallions with poor semen characteristics.  相似文献   

5.
In boars and rabbits, administration of adrenocorticotropic hormone (ACTH) results in a testis-dependent, short-term increase in concentrations of testosterone in peripheral plasma. This experiment was designed to assess the short-term effects of a single ACTH injection on plasma concentrations of testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH) and cortisol in stallions. Eight light horse and two pony stallions were paired by age and weight and then one of each pair was randomly assigned to the treatment (ACTH, .2 IU/kg of body weight) or control (vehicle) group. Injection of ACTH increased (P<.01) plasma concentrations of cortisol by approximately twofold in the first 60 minutes; control stallions showed no change (P>.10) in concentrations of cortisol during the blood sampling period. Control stallions exhibited a midday increase (P>.05) in concentrations of testosterone similar to that reported previously; ACTH treatment prevented or delayed this increase such that concentrations of testosterone in treated stallions were lower (P<.05) than in controls 4 to 5 hours after injection of ACTH. Treatment with ACTH had no effect (P<.10) on plasma concentrations of LH or FSH up to 12 hours after injection.  相似文献   

6.
Ten stallions were used to determine if the stallion responds to administration of testosterone propionate (TP) with an increase in follicle stimulating hormone (FSH) secretion after administration of gonadotropin releasing hormone (GnRH) as has been previously observed for geldings and intact and ovariectomized mares. Five stallions were treated with TP (350 μg/kg of body weight) in safflower oil every other day for 11 days; control stallions received injections of safflower oil. The response to GnRH (1.0 μg/kg of body weight) was determined for all stallions before the onset of treatment (GnRH I) and at the end of treatment (GnRH II). Blood samples were also withdrawn daily from 3 days prior to treatment through GnRH II. Treatment with TP decreased (P<.10) concentrations of FSH in daily blood samples. However, treatment with TP did not affect (P>.10) the GnRH-induced secretion of FSH. Concentrations of luteinizing hormone (LH) decreased (P<.05) in daily blood samples averaged over both groups of stallions and were lower (P<.10) in TP-treated stallions than in controls during the latter days of treatment. We conclude that TP administration to stallions does not alter the FSH response to GnRH as has been observed for geldings and for mares of several reproductive states.  相似文献   

7.
The aim of this study was to investigate the effect of gonadotrophin-releasing hormone (GnRH) immunisation on mature stallions that had been used for breeding. Four Standardbred stallions were used in the study: 3 experimental animals and 1 control animal. Semen was collected regularly, i.e. twice/week, during the 4 months prior to the experimental period. The stallions were immunised against GnRH with a GnRH-BSA conjugate. Equimune was used as the adjuvant. The stallions were immunised on 5 occasions, 4 at 2 week intervals, and the fifth 4 weeks after the fourth. Blood samples were taken once a week for analysis of GnRH antibody titre and every third week for testosterone and oestrone sulphate analyses. Semen was collected once a week, and libido and sexual behaviour were observed. Ejaculate volume, sperm concentration, total number of sperm in the ejaculate, sperm motility and sperm morphology were evaluated. Testicular size was measured once a week. At the end of the study, the stallions were castrated, and a histological examination of the testes performed. All immunised stallions produced antibodies against GnRH, and plasma testosterone concentration decreased. However, the effect of immunisation varied between stallions. In 2 of the stallions, high levels of antibodies were found, while in the third, the level was moderate. Four weeks after the first immunisation, a decrease in libido was observed. Two months after the first immunisation, marked changes in semen quality were observed in the 2 stallions with high antibody titres. Fourteen weeks after the first immunisation, the total number of sperm/ejaculate had decreased from >8.6 x 10(9) to <2.7 x 10(9), sperm motility from >59 to <10% and the frequency of morphological normal spermatozoa had decreased from >60 to <14%. The dominating abnormalities were abnormal head shapes, proximal cytoplasmic droplets and detached heads. In the third stallion, only slight changes in semen quality were found. No changes were observed in the control stallion. Decreases in testicular size were noted in all of the experimental stallions. Pronounced histological alterations in the testes were observed in 2 of the stallions. It is concluded that the vaccine was effective in stimulating production of GnRH antibodies and in suppressing testicular function and androgen secretion. However, there was an individual variation in the responses among the stallions and, further, libido was not totally suppressed.  相似文献   

8.
The long term effect of a single injection of 6,000 iu of human chorionic gonadotrophin (hCG) was studied in two pony stallions. Peripheral plasma samples were analysed for testosterone and oestrone sulphate. Testosterone concentrations were markedly elevated for five days after injection in both stallions. No adverse effects of these high concentrations were observed on concentrations later in the experiment. There was an initial increase in oestrone sulphate in one stallion, after which concentrations decreased to below pre-injection levels. The other stallion (whose initial oestrone sulphate concentrations were somewhat higher) showed no rise in response to hCG but did show a significant decline from five days after injection. Whether this suppression is an effect of the high testosterone concentrations remains to be determined.  相似文献   

9.
Six lighthorse stallions with previous sexual experience were used to determine the short-term effects of sexual stimulation (SS; 5 min exposure to an estrous mare), SS plus ejaculation (SSE), and no stimulation (control) on serum concentrations of LH, FSH, testosterone, cortisol and prolactin. Stallions received one treatment per day on d 1, 4 and 7. Treatments were assigned such that each stallion 1) received each treatment once and 2) experienced a unique sequence of treatments. Neither SS nor SSE had any consistent effects on LH or FSH concentrations. Testosterone concentrations during control bleedings increased (P less than .05) with time. This increase was suppressed (P less than .05) by both SS and SSE. Cortisol concentrations increased (P less than .05) immediately after SS and SSE. Cortisol concentrations also tended to increase during the control bleedings, but only in stallions that previously had been exposed to SS or SSE. Prolactin concentrations increased (P less than .05) immediately after SS and SSE and tended to rise during control bleedings in stallions previously exposed to SS or SSE. We conclude that 1) prolactin and cortisol were secreted rapidly in response to SS and SSE, 2) the rise in cortisol concentrations likely suppressed testosterone secretion within the next hour, and 3) stallions appeared to associate the distant sounds of other stallions with their own previous exposure to SS and SSE, resulting in a cortisol response (and perhaps a prolactin response) even in the absence of direct stimulation.  相似文献   

10.
Plasma LH and FSH concentrations were measured in mature stallions after administration of synthetic GnRH or equine pituitary extract. GnRH caused significant rises in plasma LH (2-fold) and FSH (1.7-fold). Concentrations of LH remained significantly elevated for 4 hours and FSH remained elevated for 2 hours. Similar increases in plasma LH (1.6-fold) and FSH (1.8-fold) occurred after an injection of equine pituitary extract. LH was significantly elevated for 4 hours and FSH was elevated for 6 hours.  相似文献   

11.
Influence of day length on seasonal endocrine responses were studied using stallions (seven per group). Treatments included 1) control, with natural day length; 2) 8 h light and 16 h dark (8:16) for 20 wk beginning July 16, 1982 then 16:8 from December 2, 1982 until March 5, 1984 (S-L); or 3) 8:16 from July 16, 1982 until March 5, 1984 (S-S). Blood was sampled hourly for 5 h every 4 wk; sera were pooled within horse, and luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone were quantified. Blood was collected every 20 min for 24 h every 8 wk and 2 wk before and after the December light shift. Samples were assayed for LH. Stallions in all groups underwent seasonal changes (P less than .05) in concentrations of LH, FSH, testosterone and basal concentrations of LH and amplitude of LH pulses. Season X treatment (P less than .05) reflected on early recrudescence of LH, FSH and testosterone concentrations in S-L stallions followed by earlier regression. Except for FSH hormone concentrations were depressed in S-S stallions. Number of LH pulses per 24 h was unaffected by season, treatment or their interaction. Mean amplitude of LH pulses was affected (P less than .05) by season X treatment; maximal values occurred in April vs February for control and S-L stallions, and minimal values occurred in December vs April. The season X treatment interaction (P less than .05) similarly affected basal concentrations of LH. Thus, seasonal changes in concentrations of LH, FSH and testosterone can be driven by photoperiod. Increased peripheral concentrations of LH during seasonal recrudescence of reproductive function apparently results from more LH secreted per discharge without an increased frequency of LH discharges.  相似文献   

12.
Testicular diameters and monthly blood samples were obtained from 83 stallions aged 4 to 22 years that were maintained on Central Kentucky Thoroughbred stud farms. The effects of age, season, and exposure to increased photoperiod (16 hours light/day, December 15 to April 1) on testicular diameters and plasma concentrations of FSH, LH and testosterone were studied.The results indicated that Thoroughbred stallions show distinct seasonal and age related changes in most of the reproductive parameters studied and that exposure of such stallions to increased photoperiod produced significant alterations in these changes. Although lighting stimulated testicular growth and testosterone secretion early in the breeding season such changes were short lived. Lighted stallions appeared to become refractory to the lighting program since both testicular size and plasma testosterone concentrations were significantly reduced by June.  相似文献   

13.
The effect of adrenocorticotropin hormone (ACTH) on plasma cortisol and on gonadotropin releasing hormone (GnRH)-induced release of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone was determined in nine Holstein bulls and 12 Holstein steers. Treatments consisted of animals receiving either GnRH (200 micrograms, Group G), ACTH (.45 IU/kg BW, Group A) or a combination of ACTH followed 2 h later by GnRH (Group AG). Group G steers and bulls had elevated plasma LH and FSH within .5 h after GnRH injection and plasma testosterone was increased by 1 h after GnRH injection in bulls. In Group A, plasma cortisol was elevated by .5 h after ACTH injection in both steers and bulls, but plasma LH and FSH were unaffected. In Group A bulls, testosterone was reduced after ACTH injection. In Group AG, ACTH caused an immediate increase in plasma cortisol in both steers and bulls, but did not affect the increase in either plasma LH or FSH in response to GnRH in steers. In Group AG bulls, ACTH did not prevent an increase in either plasma LH, FSH or testosterone in response to GnRH compared with basal concentrations. However, magnitude of systemic FSH response was reduced compared with response in Group G bulls, but plasma LH and testosterone were not reduced. The results indicate that ACTH caused an increase in plasma cortisol, but did not adversely affect LH or FSH response to GnRH in steers and bulls. Further, while testosterone was decreased after ACTH alone, neither ACTH nor resulting increased plasma cortisol resulted in decreased testosterone production in the bull after GnRH stimulation.  相似文献   

14.
Ten lighthorse stallions were used to determine 1) whether prolactin (PRL) and cortisol responses previously observed after acute exercise in summer would occur in winter when PRL secretion is normally low, 2) whether subsequent treatment with a dopamine receptor antagonist, sulpiride, for 14 d would increase PRL secretion and response to thyrotropin-releasing hormone (TRH) and exercise, and 3) whether secretion of LH, FSH, and cortisol would be affected by sulpiride treatment. On January 11, blood samples were drawn from all stallions before and after a 5-min period of strenuous running. On January 12, blood samples were drawn before and after an i.v. injection of GnRH plus TRH. From January 13 through 26, five stallions were injected s.c. daily with 500 mg of sulpiride; the remaining five stallions received vehicle. The exercise and secretagogue regimens were repeated on January 27 and 28, respectively. Before sulpiride injection, concentrations of both cortisol and PRL increased (P less than .05) 40 to 80% in response to exercise; concentrations of LH and FSH also increased (P less than .05) approximately 5 to 10%. Sulpiride treatment resulted in (P less than .05) a six- to eightfold increase in daily PRL secretion. The PRL response to TRH increased (P less than .05) fourfold in stallions treated with sulpiride but was unchanged in control stallions. Sulpiride treatment did not affect (P greater than .05) the LH or FSH response to exogenous GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
Three experiments were performed to test the following hypotheses: 1) stallions and/or progesterone-estradiol-treated geldings could serve as models for the effects of a single implant of the GnRH analog, deslorelin acetate, on LH and FSH secretion by mares; and 2) multiple implants of deslorelin acetate could be used as a means of inducing ovarian atrophy in mares for future study of the mechanisms involved in the atrophy observed in some mares after a single implant. In Exp. 1, nine light horse stallions received either a single deslorelin implant (n = 5) or a sham injection (n = 4) on d 0. In Exp. 2, 12 geldings received daily injections of progesterone on d -20 through -4, followed by twice-daily injections of estradiol on d -2 to 0. On the morning of d 0, geldings received either a single deslorelin implant (n = 6) or a sham injection (n = 6). Daily injections of progesterone were resumed on d 2 through 15. In Exp. 1, plasma LH and FSH were elevated (P < 0.05) in the treatment group relative to controls at 4, 8, and 12 h after implant insertion. In the treated stallions, FSH was decreased (P < 0.05) on d 3 to 13, and LH was decreased on d 6 to 13. In Exp. 2, plasma LH and FSH were elevated (P < 0.05) at 4,8, and 12 h after deslorelin implant insertion. Plasma LH was suppressed (P < 0.05) below controls on d 2 to 7, 9, and 11 to 15; plasma FSH was suppressed (P < 0.05) on d 4 to 15. In Exp. 3, 21 mares were used to determine whether multiple doses of deslorelin would cause ovarian atrophy. Mares received one of three treatments: 1) sham injections; 2) three implants on the first day; or 3) one implant per day for 3 d (n = 7 per group). Treatment with multiple implants increased (P < 0.05) the interovulatory interval by 14.8 d and suppressed (P < 0.01) LH and FSH concentrations for approximately 25 d; no mare exhibited ovarian atrophy. In conclusion, after an initial short-term increase in LH and FSH secretion, deslorelin implants caused long-term suppression of both gonadotropins in stallions as well as in geldings treated with progesterone and estradiol to mimic the estrous cycle. It is likely that either of these models may be useful for further study of this suppression in horses. Although multiple implants in mares suppressed gonadotropin secretion longer than a single implant, the lack of ovarian atrophy indicates that the atrophy observed after a single implant in previous experiments was likely due to the susceptibility of individual mares.  相似文献   

16.
An experiment was conducted to determine the effects of equine somatotropin on the reproductive axis of the stallion during the nonbreeding season. Adult stallions were treated with equine somatotropin (20 μg/kg body weight [BW]; n = 5) or saline (n = 4) daily for 21 days starting in January. During the last week of treatment, stallions were subjected to low- and high-dose injections of luteinizing hormone (LH), as well as low- and high-dose injections of gonadotropin-releasing hormone (GnRH) and thyrotropin-releasing hormone (TRH). Two months after the onset of somatotropin treatment, semen was collected from all stallions every other day for 14 days. Treatment with equine somatotropin increased (P < .001) daily IGF-1 concentrations but had no effect (P > .1) on concentrations of LH, follicle-stimulating hormone (FSH), or testosterone. The testosterone responses to injections of LH were similar (P > .1) between treatments. Likewise, the LH, FSH, prolactin, and testosterone responses to the injections of GnRH/TRH were similar (P > .1) between groups. At seminal collections, stallions treated with somatotropin exhibited greater volumes of gel-free semen (P < .01) and gel (P < .05) and had decreased time until ejaculation (P < .05). In conclusion, somatotropin treatment for 21 days may alter the long-term accessory gland contribution to seminal volume but does not appear to alter pituitary gonadotrope function or testicular testosterone secretion.  相似文献   

17.
Eight pony stallions were paired by estimated daily sperm output (DSO) and randomly assigned to one of two treatments in a randomized block experiment. Stallions received 44 μg/kg BW estradiol cypionate (ECP) or an equivalent volume of physiological saline solution on alternate days during the breeding season. Blood samples collected immediately preceding each injection were assayed for luteinizing hormone (LH), estradiol-17β (E2) and testosterone (T). Semen was collected twice weekly, 3.5 days apart, to evaluate sperm motility and total number of sperm per ejaculate. Prior to and after 4, 8 and 12 weeks on treatment, semen was collected once daily for 7 days to determine DSO. Data were separated into 9 periods (10 days each) for statistical analysis and subjected to analysis of variance for a randomized block design to determine treatment effects.There were no differences (p>.05) between groups for DSO or LH prior to initiation of treatment. Testosterone was higher (p<.05) in ECP stallions compared with C stallions prior to treatment and at all time points measured. As expected, E2 was higher (p<.05) in the ECP stallions compared to C stallions after 20 days (period 2) of treatment and for the remainder of the experiment. However, E2 was higher (p<.05) in the C group prior to treatment, but there was no difference between the groups after 10 d of treatment (period 1). ECP stallions had higher (p<.05) DSO than C stallions after 30 d on treatment. After 40 and 50 d (periods 4 and 5), ECP stallions demonstrated higher (p<.05) total sperm per period than C stallions. This was preceded by higher (p<.05) LH values for ECP stallions than for C stallions after 10 and 20 d (periods 1 and 2). No differences were found between the ECP and C groups for LH between 30 and 60 d. Although numerically higher, no significant differences (p>.05) were seen after 60 days for DSO or after 60, 70 or 80 days for total sperm per period. ECP stallions had higher (p<.05) DSO and total sperm per period after 90 d than C stallions. Additionally, LH remained significantly higher (p<.05) in the ECP group after 60 days (periods 7, 8 and 9). Elevated LH concentrations in ECP stallions demonstrated that estrogen treatment did not inhibit LH secretion in this study.  相似文献   

18.
A plasmid delivery system validated in other species was assessed for its potential for inducing long-term expression of gonadotropin-releasing hormone (GnRH) in stallions. The efficacy of this technique was demonstrated using two plasmids: pSEAP, expressing secreted embryonic alkaline phosphatase (SEAP), and pGnRH, expressing GnRH. In experiment 1, geldings were used as a model to test the effect of muscle of injection (splenius, pectoralis, and semitendinosus; n = 3 for each site) on the expression of the reporter plasmid, pSEAP. Concentrations of SEAP rose (P < .01) in jugular plasma samples, indicating uptake and expression of the pSEAP plasmid. Concentrations of SEAP were greatest (P < .05) and most consistent after pectoralis injection, and this site was chosen for injection and electroporation in the subsequent experiment. In ex-periment 2, stallions were treated with pGnRH (2 mg, n = 3; and 4 mg, n = 3) or 2 mg of pSEAP (control; n = 4) to determine the effects on the reproductive axis. Treatment with pGnRH (day 0) resulted in higher (P < .05) plasma testosterone concentrations from day 35 to 56 and increased the luteinizing hormone (LH) (P < 0.01) and testosterone (P < .1) responses to GnRH challenge on day 21. Daily semen characteristics from days 31 to 36 showed no effect (P > .1) of pGnRH treatment on seminal characteristics. It was concluded that delivery by electroporation of plasmids encoding peptide hormones may serve as a means of long-term in vivo production of peptides in the horse. Increases in LH and testosterone secretion after GnRH were observed in pGnRH-treated stallions; however, optimal conditions for expression need to be determined in future experiments.  相似文献   

19.
The objective of this study was to determine the long-term effects of the administration of 4.7-mg slow-release deslorelin implant on stallions' plasma testosterone concentrations and sexual behavior. Five control animals received a subcutaneous dose of saline solution, whereas treated animals (n = 11) received a subcutaneous implant of 4.7-mg deslorelin acetate (Suprelorin; Virbac SA, Carros, France). Testosterone plasma concentrations were monitored from April to September every week for the first 30 days, then every 2 weeks until the end of the study (98 days in total). A stimulation test using human chorionic gonadotropin was performed before and 70 days after implant administration. Behavior was assessed by asking owners to fill out a questionnaire before treatment, weekly during the study, and then at 7 months after treatment. In treated stallions, an acute increase in testosterone concentration was evident within 7 days after treatment, which was followed by a gradual decline to below basal values over the next 42 days. Results of this study support that deslorelin is biologically active in the stallion. The answers to the questionnaires showed a significant decrease (P = 0.03) in the rearing up behavior at week 3 and 4 after treatment. At the end of the study, of 11 owners, 5 asked their stallions to be reimplanted. Lacking side effects, deslorelin could be considered, in some instances, in the treatment of some behavioral problems in stallions, although there are individual variations in response, which deserve further investigations.  相似文献   

20.
Considerable variation exists in the serum levels of gonadotropins in boars; this results in differential testicular function. Boars (Chinese Meishan, European White composite, and crosses of the two breeds) selected for high and low circulating FSH concentrations were used to define possible differences in pituitary sensitivity to GnRH and GnRH antagonist and gonadal and adrenal responses. After a 2-h pretreatment sampling period, boars were injected with GnRH or GnRH antagonist and repetitively sampled via jugular cannula for changes in serum concentrations of FSH, LH, testosterone, and cortisol. In response to varying doses of GnRH or GnRH antagonist, FSH, LH, or testosterone changes were not different in high- or low-FSH boars. Declines in LH after GnRH stimulation were consistently faster in boars selected for high FSH. Chinese Meishan boars had considerably higher cortisol concentrations than White composite boars (132.2 +/- 28.5 vs 67.4 +/- 26.8 ng/mL, respectively; P < .01). When select high- and low-gonadotropin Meishan:White composite crossbreds were sampled, cortisol levels were elevated but comparable between the two groups (126.5 +/- 13.7 vs 131.4 +/- 13.4 ng/mL, respectively). After GnRH antagonist lowered LH concentrations, administration of hCG resulted in increased testosterone and cortisol concentrations. Although testosterone concentrations remained high for 30 h, cortisol concentrations returned to normal levels within 10 h after hCG injection. The mechanism by which boars selected for high gonadotropins achieve increased levels of LH and FSH may not be due to differences in pituitary sensitivity to GnRH but to differences in clearance from the circulation.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号