Dopamine agonists, anti-progestins, anti-androgens, long-term-release GnRH agonists and anti-estrogens in canine reproduction: a review

Effects of short-term oral letrozole on fresh semen parameters, endocrine balance, and prostate gland dimensions in domestic dogs

BACKGROUND

Aromatase inhibitors improve male fertility by modifying the hormonal control of spermatogenesis. The present study aimed to investigate the effects of oral administration of letrozole on testosterone and estradiol concentrations and their ratios in blood serum, seminal plasma, prostatic fluid, sperm quality in fresh semen, and prostate gland dimensions. Seven adult male intact mixed-breed dogs were selected. The animals received letrozole (72 µg/kg, PO) daily for four weeks. Blood samplings and semen collections were carried out on days 0 (control), 14 (treatment), 28 (treatment), and 42 (post-treatment).

RESULTS

Our results showed that letrozole administration resulted in a 4.3 fold significant increase in serum, seminal plasma, and prostatic fluid testosterone levels after 14 days. This remained high until the end of the study. Serum and prostatic fluid estradiol levels did not change significantly over the study period. However, the seminal plasma estradiol level showed a significant increase on day 14. The estradiol: testosterone ratio was significantly reduced on day 14 in serum, seminal plasma, and prostatic fluid samples. Letrozole significantly improved the ejaculated spermatozoa viability and concentration after 28 days of oral administration. However, the sperm plasma membrane functional integrity and kinematic parameters were not significantly affected by the treatment. Transabdominal ultrasound examination revealed a significant increase in the height, width, and volume of the prostate gland after 28 days of treatment.

CONCLUSIONS

According to the present research, oral administration of letrozole for 28 days affects local and systemic sex hormone balance leading to an improvement of the ejaculated canine spermatozoa viability and concentration concurrent with an increase in the prostate gland dimensions.

Long-lasting canine cardiovascular alterations following bromocriptine induced-estrus

Bromocriptine (BRM), a dopamine 2 receptor agonist, is a common drug for inducing estrus in dogs. It is also used for the treatment of some endocrine abnormalities and has some cardiovascular consequences in the patients under treatment. The current study aimed to evaluate its effects on the cardiovascular function of dogs during administration and the subsequent induced estrus cycle. Eight non-pregnant female dogs were assigned into control and treatment groups. The control group (n = 3) were dogs that showed proestrus naturally. The treatment group (n = 5) received oral incremental (μg/kg) doses (100 on days 1 and 2, 200 on days 3, 4, and 400 on days 5 until the proestrus expression) of BRM tablets (2.5 mg; Iran-Hormone Co, Iran). The left ventricle function, carotid blood flow indices, and systolic (SAP) and diastolic (DAP) arterial pressure were recorded every two days. The phases of the cycle were determined using a vaginal smear. Peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistance index (RI) had a sharp decline following the administration of BRM (P < 0.05). The carotid PSA, EDV, RI, and pulse index were lower during induced estrus compared to the control (p < 0.05). BRM-induced estrus showed a different pattern of changes compared to the normal cycle from day 9 (p < 0.05) onwards. The cardiovascular effects of BRM remained for days after the termination of administration which may interfere with reproductive functions.

Effect of drugs on fertility in male dogs: A review

The aim of this literature review is to present and discuss the available data on the effects of drugs on male dog fertility. Apart from hormones and antihormonal agents, there is still only little information available regarding the effect of other drugs on sexual function and fertility in male dogs. A negative impact on fertility in male dogs has been reported for vincristine, cyclophosphamide, tetracycline and ketoconazole. However, preclinical safety studies of drugs for human use indicated that spermatogenesis in dogs may be sensitive to a wide variety of drugs. Thus, in cases of reduced fertility or infertility in male dogs, medical treatment should always be considered. In most cases, the effects of drugs on sexual function and spermatogenesis are reversible after the discontinuation of the drug. Further studies on the effects of drugs on male dog fertility are needed.

Relationship between clinical signs and hormonal analytical findings in bitches with lactatio sine graviditate

OBJECTIVE

Lactatio sine graviditate of the bitch can become clinically relevant in particularly severe manifestations. The aim of the study was to relate the hormone pattern consisting of progesterone (P4), estradiol 17β (E2) and prolactin to the time of occurrence of lactatio sine graviditate in the course of metoestrus and anoestrus as well as to its symptomatology.

MATERIAL AND METHODS

Sixty-eight bitches with apparent lactatio sine graviditate were divided into 3 groups according to their cycle status. All bitches were examined for gynaecological findings. Furhtermore, their blood progesterone, oestrogen, and prolactin concentrations were determined and compared with the 133-day hormone profile of 7 control animals.

RESULTS

Lactatio sine graviditate occurring in early metoestrus was characterised more by a shifted P4:E2 ratio than by hyperprolactinaemia. Overall, the prolactin concentration in the peripheral blood was significantly increased. Analysis of the individual cases revealed that hyperprolactinaemia was present to varying degrees. It could be detected in almost all bitches that showed full symptomatology at the end of metoestrus or at the beginning of anoestrus. Only then clinical signs correlated with an increased prolactin concentration in the peripheral blood. In most cases, the estradiol-17β concentration was within the reference range.

CONCLUSION AND CLINICAL RELEVANCE

The study indicates that the administration of prolactin inhibitors alone is not indicated in all cases of lactatio sine graviditate and that the timepoint of onset of the clinically relevant symptoms and the current prolactin level should be taken into account in the treatment of affected bitches.

Prostatic hyperplasia: Vascularization, hemodynamic and hormonal analysis of dogs treated with finasteride or orchiectomy

As a consequence of a hormonal imbalance, Prostatic Hyperplasia (PH) is characterized by increased prostate volume, along with higher local angiogenesis and vascularization. Orchiectomy is the common treatment for dogs, however it is not an option for breeding animals. Thus, finasteride arises as the drug of choice for stud dogs. Therefore, the aim of this study was to evaluate the effects of orchiectomy or finasteride therapies on hormonal and vascular dynamics of PH dogs. Fifteen dogs, aged 6–13 years were assigned to: Untreated Group (dogs diagnosed with PH—n = 5), Finasteride treated group (PH dogs treated with finasteride—n = 5) and Orchiectomy treated group (PH dogs submitted to orchiectomy–n = 5). Evaluations were performed in a monthly interval (first day of treatment; after 30 and 60 days). Doppler ultrasonography was performed to measure prostatic volume, vascularization and hemodynamic profile of prostatic artery. Dihydrotestosterone, estrogen and testosterone concentrations were measured. At day 60, prostatic biopsy was performed for histological, immunohistochemical and qPCR analysis for VEGF-A expression. At day 60, vascularization score was higher in untreated compared to treated groups (finasteride and orchiectomy). Furthermore, VEGF-A expression was lower in the Orchiectomy Treated Group, but VEGF-A was immunohistochemically lower in both treated groups (finasteride and orchiectomy) compared to the Untreated Group. The efficiency of finasteride treatment in reducing clinical signs, prostate volume and vascularization appears to be similar to orchiectomy. In conclusion, both PH medical and surgical therapy lead to reduction in prostate dimension and VEGF-A expression and, consequently, lower local vascularization. However, orchiectomy promotes marked hormonal changes, which ultimately lead to prostate atrophy.

Administration of aromatase inhibitor MPV-2213ad to blue fox vixens (Vulpes lagopus) as a model for contraception in female dogs

The interest in non-surgical approaches to contraception and fertility control in female dogs has increased in recent years. In this study the effect of an aromatase inhibitor (finrozole) was evaluated in fur production animals, farmed blue fox vixens, as a model for contraception in bitches. A total of 80 vixens were divided into 4 groups, receiving orally placebo (A) or finrozole 0.5 mg/kg (B), 3.5 mg/kg (C) or 24.5 mg/kg (D) for 21 consecutive days beginning in the pre-ovulatory period of heat. Monitoring of the vixens included clinical signs of heat, measurement of vaginal electrical resistance (VER) as well as oestradiol and progesterone concentrations in plasma. The approximate relation of the start of treatment to ovulation varied from 11 days before to one day after ovulation provided that the LH peak occurred 0.5-2 days before the VER peak and ovulation was then estimated to occur 2 days after the LH peak. Seventy vixens were artificially inseminated within 8 h after a 50 Ω decline in vaginal electrical resistance was detected. Ten vixens were not inseminated. Pregnancy was confirmed by transabdominal ultrasound examination and birth of cubs was recorded. The pregnancy rates in the groups were 89.5% (A), 81.3% (B), 55.6% (C) and 52.9% (D). The average number of live born pups in the four groups was 9.4 (A), 7.0 (B), 5.8 (C), and 3.8 (D), respectively. No deleterious effects (for instance malformations) of finrozole on pups could be verified. The administration of finrozole did not have a significant effect on oestradiol parameters and VER values in vixens. Progesterone values were significantly higher in treatment groups compared with the placebo group. The results indicate that pregnancy could be avoided by finrozole provided that doses of ≥3.5 mg/kg were used and the treatment was initiated at least four days before the day of artificial insemination. This corresponds with two to six days before ovulation provided that the LH peak occurred 0.5-2 days before the VER peak and that ovulation then occurred in average 2 days after the LH peak.

A Rare Case of Idiopathic Pyometra in a Premenopausal Patient

Pyometra is a very uncommon disease principally occurring in postmenopausal women. It is characterized by the accumulation of purulent material within the uterine cavity. This paper presents the clinical history of a 35-year-old premenopausal woman with otherwise normal menstruation who developed heavy menstruation and was diagnosed with a benign pyometra of indeterminate etiology in March 2017. The patient underwent repeated ultrasound-guided drainage, dilation and curettage, and antibiotic therapy. Biopsies of the pelvic sidewall revealed endometriosis in June 2017. The heavy menstruation and suppurative fluid in the uterus of the patient persisted in which intramuscular leuprolide acetate was prescribed to address the endometriosis and heavy menstrual bleeding. Ultimately, the leuprolide acetate effectively resolved the patient's bleeding and pyometra. The medication was concluded after 12 months of supervision and the patient is currently symptom free. Pyometra is an unusual condition rarely identified in premenopausal women. Drainage and antibiotic therapy are routinely employed; however, one may consider gonadotropin-releasing hormone agonist medication to potentially confer a beneficial patient outcome in rare cases where endometriosis and bleeding are intractable.

Canine pseudopregnancy: an evaluation of prevalence and current treatment protocols in the UK

BACKGROUND

There is a dearth of literature on pseudopregnancy in the bitch, with only a few treatment-based studies published since the 1990s. Pseudopregnancy may be under-recognised in bitches and may account for a proportion of behavioural cases seen in veterinary practices including aggression. Little is known about commonly used treatments for overtly pseudopregnant bitches and it is possible that current regimes may not be prescribed for a sufficient duration to control any clinical signs including, physical and behavioural changes. To investigate current trends in diagnosis and treatment of canine pseudopregnancy, a postal survey was sent to 2000 randomly selected veterinary surgeons in UK veterinary practices. The questionnaire queried how often vets recognise cases of pseudopregnancy in spayed and entire bitches, which physical or behavioural signs are commonly recognised for diagnosis, and which management or treatment protocols are used.

RESULTS

The response rate was 19.8% (397/2000). Ninety-six percent of veterinary surgeons reported seeing pseudopregnant bitches showing behavioural changes without any physical changes within the last 12 months. Of those behavioural changes, collecting and mothering objects was the most frequently reported behavioural sign (96%). Ninety-seven percent of vets had seen aggression in pseudopregnant bitches. Nevertheless, only 52% of vets routinely asked owners about behavioural changes during consultations. Forty-nine percent of respondents reported seeing pseudopregnancy in spayed bitches. The most commonly reported physical sign was enlarged mammary glands and/or milk production (89%). Treatment options varied (surgical, medical or none) and depended on duration and severity of physical and behavioural signs, owners' preference, cost, concurrent disease, drug availability and previous history.

CONCLUSIONS

This is the largest epidemiological study of canine pseudopregnancy in the UK. The prevalence and severity of clinical signs in dogs with pseudopregnancy are variable and possibly under-estimated. Dogs with overt pseudopregnancy experience diverse physical and behavioural changes and information on standard treatment protocols are lacking. Although, progress on our understanding of diagnosis and treatment of pseudopregnancy in spayed and entire bitches has been made, further studies are warranted.

Effects of GnRH vaccination in wild and captive African Elephant bulls (Loxodonta africana) on reproductive organs and semen quality

OBJECTIVES

Although the African elephant (Loxodonta africana) is classified as endangered by the International Union for Conservation of Nature (IUCN), in some isolated habitats in southern Africa, contraception is of major interest due to local overpopulation. GnRH vaccination has been promoted as a non-invasive contraceptive measure for population management of overabundant wildlife. We tested the efficacy of this treatment for fertility control in elephant bulls.

METHODS

In total, 17 male African elephants that were treated with a GnRH vaccine were examined in two groups. In the prospective study group 1 (n = 11 bulls, ages: 8-36 years), semen quality, the testes, seminal vesicles, ampullae and prostate, which were all measured by means of transrectal ultrasound, and faecal androgen metabolite concentrations were monitored over a three-year period. Each bull in the prospective study received 5 ml of Improvac® (1000 μg GnRH conjugate) intramuscularly after the first examination, followed by a booster six weeks later and thereafter every 5-7 months. In a retrospective study group (group 2, n = 6, ages: 19-33 years), one examination was performed on bulls which had been treated with GnRH vaccine for 5-11 years.

RESULTS

In all bulls of group 1, testicular and accessory sex gland sizes decreased significantly after the third vaccination. In six males examined prior to vaccination and again after more than five vaccinations, the testis size was reduced by 57.5%. Mean testicular height and length decreased from 13.3 ± 2.6 cm x 15.2 ± 2.8 cm at the beginning to 7.6 ± 2.1 cm x 10.2 ± 1.8 cm at the end of the study. Post pubertal bulls (>9 years, n = 6) examined prior to vaccination produced ejaculates with viable spermatozoa (volume: 8-175 ml, sperm concentration: 410-4000x106/ml, total motility: 0-90%), while after 5-8 injections, only 50% of these bulls produced ejaculates with a small number of immotile spermatozoa. The ejaculates of group 2 bulls (vaccinated >8 times) were devoid of spermatozoa. Faecal androgen metabolite concentrations measured in captive males decreased significantly after the fourth vaccination. None of the males entered musth during the treatment period.

CONCLUSIONS

Our results showed a marked decrease in semen quality, testicle and secondary sex gland sizes following repeated GnRH vaccinations. After 2-4 years of continuous treatment every 5-7 months, the effects were similar to surgical castration.

Effect of deslorelin on testicular function, serum dihydrotestosterone and oestradiol concentrations during and after suppression of sexual activity in tom cats

Objectives The aim of the study was to evaluate the efficacy of a 4.7 mg deslorelin implant in tom cats. Methods Nine mature male cats were included in the deslorelin group and five cats in the control group. Before the study started, all cats were confirmed to have distinct sexually dimorphic behaviour. Blood samples were taken on the implantation day, at day 7 and at day 15, then monthly, in order to measure serum dihydrotestosterone (DHT) and 17beta(β)-oestradiol concentrations. The deslorelin group (n = 9) was divided into two subgroups: five cats (cats 1-5) were neutered in the postimplantation period during suppression of sexually dimorphic behaviour, and four cats (cats 6-9) were neutered after re-expression of sexually dimorphic behaviour. The control group cats (n = 5) were castrated without administration of the implant. Results Sexually dimorphic behaviours ceased within a mean ± SD of 13-58 days (23.30 ± 14.17) after implantation. DHT concentration decreased within 30 days. The mean duration of suppression was 26.5 ± 7.42 months and reactivation coincided with increased DHT values reaching preimplantation concentrations within 1 month. 17β-oestradiol concentrations significantly correlated with DHT concentrations ( P <0.01). For cats castrated during suppression of sexual behaviour, the length of the long axes of the nuclei of Leydig cells, the diameter of seminiferous tubules and the height of the epithelium of the seminiferous tubules did not change until 3-6 months after implantation, whereas at 12 and 32 months the measured values were even lower than in the control group. For cats castrasted after reactivation, the length of long axes of the nuclei of Leydig cells and the diameter of seminiferous tubules approached the values of the control group between 4 and 6 months after reactivation. Conclusions and relevance A deslorelin implant (4.7 mg) suppresses sexually dimorphic behaviour in tom cats without any side effects and with full reversibility; however, duration of suppression is highly individual.

Multiparametric Phenotypic Screening System for Profiling Bioactive Compounds Using Human Fetal Hippocampal Neural Stem/Progenitor Cells

Stem cell research has been progressing rapidly, contributing to regenerative biology and regenerative medicine. In this field, small-molecule compounds affecting stem cell proliferation/differentiation have been explored to understand stem cell biology and support regenerative medicine. In this study, we established a multiparametric screening system to detect bioactive compounds affecting the cell fate of human neural stem/progenitor cells (NSCs/NPCs), using human fetal hippocampal NSCs/NPCs, HIP-009 cells. We examined effects of 410 compounds, which were collected based on mechanisms of action (MOAs) and chemotypes, on HIP-009’s cell fate (self-renewal, neuronal and astrocytic differentiation) and morphology by automated multiparametric assays and profiled induced cellular phenotypes. We found that this screening classified compounds with the same MOAs into subgroups according to additional pharmacological effects (e.g., mammalian target of rapamycin complex 1 [mTORC1] inhibitors and mTORC1/mTORC2 dual inhibitors among mTOR inhibitors). Moreover, it identified compounds that have off-target effects under matrix analyses of MOAs and structure similarities (e.g., neurotropic effects of amitriptyline among tri- and tetracyclic compounds). Therefore, this automated, medium-throughput and multiparametric screening system is useful for finding compounds that affect the cell fate of human NSCs/NPCs for supporting regenerative medicine and to fingerprint compounds based on human stem cells’ multipotency, leading to understanding of stem cell biology.

Genotoxicity of the some selective estrogen receptor modulators: a review

The objective of this article is to review genotoxicological profile of the major selective estrogen receptor modulators, including clomiphene, tamoxifen, toremifene, raloxifene. These drugs have been used for infertility treatment and breast cancer prevention in high risk-women. However, some studies reported that especially tamoxifen is a genotoxic agent and is related with endometrial cancer. Our review indicate that clomiphene and tamoxifen were found as genotoxic agent in majority of the tests. However published reports showed that toremifene is a weakly genotoxic agent. The genotoxic effects of raloxifene are still poorly known. Further genotoxicity studies should be conducted especially for raloxifene.

Scientific and Regulatory Policy Committee (SRPC) Paper

Hormonally mediated effects on the female reproductive system may manifest as pathologic changes of endocrine-responsive organs and altered reproductive function. Identification of these effects requires proper assessment, which may include investigative studies to profile female reproductive hormones. Here, we briefly describe normal hormonal patterns across the estrous or menstrual cycle and provide general guidance on measuring female reproductive hormones and characterizing hormonal disturbances in nonclinical toxicity studies. Although species used in standard toxicity studies share basic features of reproductive endocrinology, there are important species differences that affect both study design and interpretation of results. Diagnosing female reproductive hormone disturbances can be complicated by many factors, including estrous/menstrual cyclicity, diurnal variation, and age- and stress-related factors. Thus, female reproductive hormonal measurements should not generally be included in first-tier toxicity studies of standard design with groups of unsynchronized intact female animals. Rather, appropriately designed and statistically powered investigative studies are recommended in order to properly identify ovarian and/or pituitary hormone changes and bridge these effects to mechanistic evaluations and safety assessments. This article is intended to provide general considerations and approaches for these types of targeted studies.

Morphological examination of the corpora lutea from pregnant bitches treated with different abortifacient regimes

Different abortifacient regimes in dogs were analysed for their effect on the pregnancy corpora lutea (CL), namely, prostaglandin F2a analogue cloprostenol (CLO) combined with dopamine agonist cabergoline (CAB), or progesterone (P4) receptor antagonist aglepristone (AGL). Ovaries were collected after 6-10 days of treatment during first trimester. The CL of the control-group showed strong expression of relaxin (RLX), its receptor RXFP1 and enzymes of steroid biosynthesis (HSD) with high peripheral P4-levels. Whereas RXL, RXFP1 and HSD were lowest expressed in the CLO/CAB-group with a massive degeneration of CL and their blood vessels combined with low peripheral P4-level. The AGL-group showed less extensive CL degeneration and more intensive staining of the examined factors than CLO/CAB. In summary, all examined factors are associated with normal luteal function and are useful tools to stage luteolysis. Although both treatments have the same abortive action, their sequence of events on the CL is different.

Follow-up examinations after medical treatment of pyometra in cats with the progesterone-antagonist aglepristone

The aim of this study was to determine the therapeutic success of the medical treatment of pyometra with the antigestagen aglepristone and to document the recurrence rate in relation to the time interval after treatment with antigestagens in cats. Ten cats, 2-13 years of age and nulliparous were used in the study. The cats were treated with aglepristone at a dose of 10mg/kg body weight subcutaneously on days 1, 2, 7 and 14 (if not cured). In addition, trimethoprim/sulphadoxine was also administered at a dose of 15mg/kg body weight subcutaneously once a day for 7 days. Nine out of the 10 cats responded well to treatment. No recurrence was observed in a follow-up period of 2 years. No side effects were observed. The data suggest that aglepristone treatment is a promising approach for the medical treatment of pyometra in cats.

Canine prostatic disease: a review of anatomy, pathology, diagnosis, and treatment

Disease conditions affecting the canine prostate gland are encountered frequently in small animal practice. The most common conditions affecting the canine prostate include benign prostatic hyperplasia, prostatitis, prostatic cysts, and prostatic neoplasia. Clinical signs associated with each of these conditions often overlap; therefore, it is important to reach a definitive diagnosis prior to initiating treatment. This paper reviews the diseases associated with the prostate gland of the dog, their diagnosis, as well as current treatment options for management of these conditions. Emphasis is placed on proper diagnostic sampling of the prostate gland, its fluid, and interpretation of findings, as well as emerging medical options for treatment of canine prostatic disease.

A combination of oral cabergoline and double cloprostenol injections to produce third-quarter gestation termination in the bitch

To assess the efficacy and safety of a combined cabergoline and cloprostenol protocol to terminate third-quarter pregnancy, 22 pregnant bitches that ranged from 35 to 45 days after mating were randomly assigned to a treatment group (n=13) or to an untreated control group (n=9). The animals were monitored for 12 days, and pregnancy termination was confirmed by ultrasound examination. Twelve of the 13 treated bitches aborted within 9 days of the initiation of treatment (mean 4.6 days). Only mild side effects were observed. The control animals had normal gestational courses, as did the bitch that did not respond to the therapy. This combination of drugs appeared to be a practical, safe, and efficient abortifacient when used in third-quarter pregnancies.