Concentrations of progesterone, prolactin and relaxin in the luteal phase and pregnancy in normal and short-cycling German Shepherd dogs

New horizons in the reproductive biology of Chinese pangolin (Manis pentadactyla) using the gonadal hormonal profile

The reproductive uniqueness of pangolins has been documented through diverse biological reports with discernible data discrepancies in gestation, copulation, and pregnancy. These mechanistic reproductive differences have yet to be endocrinologically quantified, which could assist in optimizing natural breeding in zoos to recover endangered species. The present research characterizes the Chinese pangolin's annual seasonal reproductive pattern by measuring immunoreactive estrogens and progestagens in 34 captive females and testosterone in 29 captive males. Our results showed that Chinese pangolins are seasonal breeders, with most births witnessed during Sept-Dec, overlapping with the field records. Females exhibited spontaneous ovulation and post-partum ovulation. Pregnant females exhibited a higher P4 level for ~ 9 months (Jan-Sept) and decreased before parturition (Oct-Dec). The circulating E2 is maintained at the baseline in pregnant females year-round. Contrastingly, in non-pregnant females, P4 is maintained at the baseline, apart from a slight elevation in January, and E2 demonstrates a sudden hike from November and remains elevated until February, suggesting the onset of ovulation. The serum testosterone concentration in males peaked during October, which is in sync with the female ovulation period. As a result that their major reproductive events, ovulation, mating, and parturition, all transpire in November-March. Evidence also supports that Chinese pangolins exhibit signs of postimplantation (pregnancy) ranging only from 5 to 6 months (May-Oct), preceded by possible facultative delay implantation triggered by lactation. The provided data not only fill in the knowledge gap for this critically endangered species but can also assist in making informed decisions, which can directly affect the successful breeding of this species in captivity.

Causes of pregnancy arrest in the canine species

In the canine species, early pregnancy arrest before 30-40 days of pregnancy will induce intra-uterine embryonic or foetal resorption, with very few clinical signs. If no genital examination by ultrasound is performed at that time, it will often remain unnoticed and the bitch will be qualified as infertile. It is only when pregnancy stops at a later stage, mostly after 40 days, that clinical signs will be seen. Expulsion of aborted foetuses or placentas may be observed, although the dam frequently eats the expelled tissues. Intra-uterine mummification may also occur. This article reviews the causes of pregnancy termination in the bitch, both at the embryonic and the foetal stages, reported in the literature. Canine brucellosis is by far the most important disease concerned in this aspect. There is an important current concern about this disease, due to the fact that several outbreaks have been observed recently in Europe, and that it is a very contagious disease; it may be an underestimated zoonosis. Other bacterial causes of pregnancy arrest are sporadic. There is, however, a growing attention towards the microbiological content of raw food diets which are more and more popular among dog breeders and may-if badly prepared-contain abortifacient bacteria such as Campylobacter jejuni or Listeria monocytogenes. The abortifacient role of endogenous vaginal bacteria and mycoplasms remains unclear and may be related to an imbalanced vaginal flora with subsequent ascending bacterial contamination of the uterus. The role of Canine Herpesvirus on abortion is controversial and probably not frequent. Other viruses have been shown experimentally to induce abortion but their natural occurrence in this respect remains unknown. The same applies to the parasite Neospora caninum which is suspected, but not proven, potentially to induce pregnancy arrest in bitches. Among non-infectious causes, uterine pathology such as cystic endometrial hyperplasia (CEH) or sub-clinical post-mating endometritis which can cause infertility and may also induce embryonic resorption. The role of luteal insufficiency in pregnancy arrest is probably overestimated.

Influence of a Single Dose of Meloxicam Administrated during Canine Estrus on Progesterone Concentration and Fertility-A Clinical Case Study

This case report presents an observation of the influence of meloxicam administration, during the periovulatory phase, on corpora lutea function in the domestic dog (Canis familiaris). A 2 year old female German Shepherd dog, with a level of progesterone suggestive of the periovulatory period (5.97 ng/mL), received a single subcutaneous injection of meloxicam (0.2 mg/kg body weight). In this female, subsequent evaluation to detect the optimal time for mating revealed a strong decrease in P4 (2.77 ng/mL), although it increased to 13.98 ng/mL within the following three days. The same female conceived and delivered a litter of the same size as in a subsequent cycle where meloxicam was not administered. The use of NSAID (nonsteroidal anti-inflammatory drugs), and particularly meloxicam, as a COX-2 inhibitor that influences the production of prostaglandins has been reported as being potentially harmful for ovulation and pregnancy in various species, including humans. In dogs, the secretion of prostaglandin E (PGE) is thought to be important for ovulation and the formation of the corpora lutea, the only source of P4, which is required for pregnancy maintenance. Although previous case reports have indicated an influence of meloxicam administration on CL function in domestic dogs, here, the decreased progesterone level observed directly after a single dose of meloxicam was only temporary, with no negative impact on fertility. Based on our observations, further studies related to the influence of the timing of meloxicam administration on ovarian cycle advancement, as well as the influence of duration of treatment, dosage, and route of administration on progesterone levels, as an indicator of CL function, are required.

Progesterone Concentrations during Canine Pregnancy

Simple Summary

For breeders and bitches alike, pregnancy is a challenging period. Insufficient serum progesterone concentrations have frequently been suggested to be responsible for pregnancy loss or early parturition, without any scientific evidence to support those claims. In this study, a large number of bitches was followed throughout pregnancy, and serum progesterone concentrations were determined to deduce which concentrations could be considered normal. Three blood samples were collected, one each during early, mid and late pregnancy. The results indicated that progesterone concentrations can be lower than previously described as adequate in the veterinary literature, with the bitch still exhibiting no signs of pregnancy distress and giving birth to healthy puppies at the expected time.

Abstract

Pregnancy and lactation are amongst the most challenging times of a bitch’s life. Most studies focusing on the endocrinological aspect of pregnancy consider only a small number of animals. The aim of this study was to evaluate progesterone (P4) concentrations in a large number of bitches during early, mid and late pregnancy. In total, 126 bitches of various breeds were recruited following a thorough clinical and gynecological examination during estrus. Blood samples were collected three times (T1–T3) during pregnancy or from non-pregnant dogs in diestrus, and P4 was measured via chemiluminescence. At T1 (11–19 days post-ovulation (dpo)), serum P4 concentrations were 30.23 ± 6.65 ng/mL and 28.45 ± 6.26 ng/mL, at T2 (23–32 dpo) they were 22.73 ± 6.27 ng/mL and 22.59 ± 5.77 ng/mL and at T3 (52–60 dpo) they were 6.68 ± 2.18 ng/mL and 3.17 ± 2.26 ng/mL, in pregnant (n = 98) and non-pregnant (n = 23) dogs respectively. The P4 concentrations differed significantly between pregnant and non-pregnant animals at the last examination (p ≤ 0.001). In the context of hypoluteoidism, the gathered data yielded interesting results. Overall, 28 out of 98 pregnant bitches showed a greater decline (>15 ng/mL) in P4 concentrations from early to mid-pregnancy, and 56 bitches showed P4 concentrations lower than deemed adequate (>20 ng/mL at T1 and T2, >5 ng/mL at T3) according to existing recommendations. Despite not being supplemented with P4, none of those animals suffered from abortion or preterm delivery. Considering that supplementation of P4 can entail considerable risks for the bitch and the puppies, more research on P4 concentration patterns, diagnosis of hypoluteoidism and treatment indications and options is indicated.

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.

Comparison of a Point-of-Care Analyzer With a Chemiluminescent Immunoassay for Serum Progesterone Measurement in Breeding Management of the Bitch

Accurate serum progesterone measurements for timing bitches during breeding management is critical for reproductive practice, especially as artificial insemination has become routine to facilitate breeding of animals that are geographically or temporally separated. To measure serum progesterone, chemiluminescent immunoassay (CLIA) has replaced radioimmunoassay as the current standard in the bitch due to its high correlation and increased practicality. In January 2019, a colorimetric point-of-care (POC) immunoassay for quantitative in-clinic canine serum progesterone measurements in <30 min was released. This study provides an independent comparison of the POC (Catalyst One, IDEXX) to the current industry standard, CLIA (Immulite-2000, Siemens). To assess inter-assay imprecision of POC and agreement of the POC and CLIA results, 100 canine serum samples were analyzed on three analyzers (POC-1, POC-2, and CLIA), of which, 74 (POC-1) and 75 (POC-2) results were within POCs' reportable range of 0.2–20 ng/mL and included in the study. To assess intra-assay imprecision, pooled canine serum samples at low (L1), intermediate (L2), and high (L3) progesterone concentrations were analyzed ten times each on POC-1 and CLIA. Relative to CLIA, POC values showed good correlation (POC-1, r² = 0.9366; POC-2, r² = 0.9438, P < 0.0001) and significant positive proportional bias at values >2 ng/mL. The POC inter-assay coefficients of variation (CVs) were 13.2% (0.2–2.9 ng/mL, 0.6–9.2 nmol/L, L1), 10.0% (3.0–9.9 ng/mL, 9.5–31.5 nmol/L, L2), 7.1% (10.0–20.0 ng/mL, 31.8–63.6 nmol/L, L3), and 11.2% (all samples). The intra-assay CVs for POC (L1, 15.3%; L2, 7.0%; L3, 4.7%) were higher than those for CLIA (L1, 5.89%; L2, 4.89%; L3, 3.44%). Based on the more rapid increase in serial serum progesterone concentrations in ovulating bitches and the greater imprecision of the POC, the clinical interpretations of serum progesterone measurements as they relate to canine breeding management should be made with caution.

Endometrial receptivity and embryo implantation in carnivores-commonalities and differences with other mammalian species

Endometrial receptivity and embryo implantation processes are a major point of pregnancy failure in many mammalian species, including humans. Although reproductive biology in many carnivore species remains enigmatic, the few that have been studied so far are invaluable comparative models. The goals of this review are to (1) summarize current data on the mechanisms involved in uterine receptivity and embryo implantation in carnivores, including commonalities and differences with other mammalian species and (2) identify research priorities to better understand a key phenomenon in a critical group of mammals. Besides unique reproductive traits in some carnivores (induced vs. spontaneous ovulation in cats, ovulation at the germinal vesicle stage in dogs), preimplantation embryo development is comparable with other orders. However, the timing of implantation varies, especially in species having an embryonic diapause. Mechanisms involved in endometrial receptivity and decidualization still remain to be fully understood, but specific markers have already been identified. Importantly, the use of endogenous hormones to control the ovarian activity may impact endometrial receptivity and subsequent embryo implantation. Next, research efforts should take advantage of advanced technologies to further study embryo implantation in carnivores and to provide more relevant models to reproductive medicine or for the conservation of rare and endangered species.

Canine conceptus-maternal communication during maintenance and termination of pregnancy, including the role of species-specific decidualization

Among domestic animal species, the reproductive biology of the dog belongs to the most peculiar. This includes the conceptus-maternal communication and endocrine mechanisms involved in maintenance of pregnancy. Dogs fully depend on luteal progesterone (P4) throughout pregnancy, with similar steroid secretion patterns in pregnant and non-pregnant bitches until prepartum luteolysis. Thus, dogs lack the classical recognition of pregnancy. The luteal P4 is the most important hormone regulating the onset and maintenance of pregnancy in previously estrogenized bitches. Although the canine uterus is exposed to high P4 levels, decidualization is not spontaneous but induced by the presence of embryos. Following implantation, decidualization continues, associated with development of the invasive endotheliochorial placenta, leading to establishment of maternal decidual cells expressing the nuclear P4 receptor (PGR). Consequently, although not producing steroids, the canine placenta remains highly sensitive to circulating ovarian steroids. The placental conceptus-maternal communication is responsible for the maintenance of pregnancy, with functional withdrawal of PGR evoking a luteolytic cascade with prepartum PGF2α release. The fetal trophoblast is the major source of prepartum placental prostaglandins. This conceptus-maternal communication is unique to the dog and has clinical implications. Due to luteal steroids, there is no prepartum estradiol increase. Elevated cortisol levels are observed irregularly. This emphasizes the unique character of canine reproductive physiology and the challenges in transferring translational research to the dog. Further research is needed for better understanding of canine reproduction and improving clinical protocols, including the latest results obtained from applying modern laboratory technologies such as the transcriptomic approach.

Sensitivity of the fasciae to sex hormone levels: Modulation of collagen-I, collagen-III and fibrillin production

Although it is now recognized that women suffer from myofascial pain to a greater extent than men, and that the muscular fasciae can respond to hormonal stimuli, thanks to the expression of sex hormone receptors, how the fasciae can modify their structure under hormonal stimulation is not clear. In this work, an immunocytochemical analysis of collagen-I, collagen-III and fibrillin were carried out on fibroblasts isolated from human fascia lata after in vitro treatment with various levels of sex hormones β-estradiol and/or relaxin-1, according to the phases of a woman's period (follicular, periovulatory, luteal, post-menopausal phases and pregnancy). This study demonstrates for the first time that fascial cells can modulate the production of some components of the extracellular matrix according to hormone levels, when treated with β-estradiol: collagen-I falls from 6% of positivity in the follicular phase to 1.9 in the periovulatory phase. However, after the addition of relaxin-1 to the cell culture, the production of extracellular matrix decreased and remained at the same level (1.7% of collagen-I, at both follicular and periovulatory levels of hormones). These results confirm the antifibrotic function of relaxin-1, thanks to its ability to reduce matrix synthesis. They are also a first step in our understanding of how some hormonal dysfunctions in women can cause a dysregulation of extracellular matrix production in fasciae.

Hypoluteoidism in a dog associated with recurrent mammary fibroadenoma stimulated by progestin therapy

Background

Hypoluteoidism in the bitch is characterized by insufficient production and secretion of progesterone by the corpora lutea. It is a rare pathologic condition and during pregnancy, it leads to embryonic resorption or fetal abortion. Supplementary therapy with progestins is indicated during pregnancy to obtain delivery of vital puppies but unwarranted side effects of such treatment are poorly documented.

Case presentation

A 4-year-old, nulliparous, female Istrian Shorthaired Hound dog had been mated repeatedly in six heats with different dogs of proven fertility but signs of pregnancy did not develop. Estrous cycles, mating and pregnancies were monitored as hypoluteoidism or genital disease was suspected. During the first monitored estrus, the bitch was mated and on day 18 [day 0, day of estimated peak of luteinizing hormone (LH)], ultrasound examination showed three amniotic vesicles that were however found to be resorbed between day 20 and 23. Progesterone concentrations, measured by ELISA, were >8 ng/mL until day 12 and 1–2.5 ng/mL on days 20, 23 and 26. Primary hypoluteoidism was therefore suspected. In the second monitored estrus, the bitch was mated and during pregnancy, progesterone concentrations were >8 ng/mL until day 17 and 1–2.5 ng/mL on day 19. On days 20 and 22, two out of three embryonic vesicles had been resorbed. The bitch was treated with progesterone in oil from day 19 to day 58. Increase in the size of 2nd left thoracic mammary gland (T2-L) was observed and on day 46, ultrasound evaluation and biopsy were performed revealing a low-cellularity fibroadenoma. Parturition started spontaneously at day 65 but due to dystocia caused by fetal macrosomia, a Caesarean section was performed. During the next (third) monitored estrus, the bitch was bred again and during pregnancy, early decrease in progesterone concentration confirmed the diagnosis of primary hypoluteoidism. The bitch was treated with synthetic progestin (altrenogest) from day 8 to day 57. Five amniotic vesicles were detected by ultrasonography. Recurrence of swelling of T2-L was observed. On day 60, the bitch whelped five pups, two males and three females. As reported later by the owner, the latter did not show any sign of heat over the past 3 years. In one of them, clitoral hypertrophy and a blind ending vagina were diagnosed.

Conclusions

This is the first description of early hypoluteoidism in a pregnant bitch developing a mammary fibroadenoma under progestin treatment.

Functional implications of the utero-placental relaxin (RLN) system in the dog throughout pregnancy and at term

Relaxin (RLN) is a key hormone of pregnancy in mammals best known for its involvement in connective tissue remodeling. In the domestic dog, placental RLN is the only known endocrine marker of pregnancy. However, knowledge is sparse regarding the spatio-temporal expression of RLN and its receptors (RXFP1 and RXFP2) in the canine uterus and placenta. Here, their expression was investigated in the pre-implantation uterus and utero-placental compartments (UtPl) at selected time points during gestation: post-implantation, mid-gestation, and at normal and antigestagen-induced luteolysis/abortion. Immunohistochemistry with newly generated, canine-specific antisera, in situ hybridization and semi-quantitative PCR were applied. In compartmentalization studies, placental and endometrial RLN increased continuously toward prepartum. The placental RXFP1 was time-related and highest during post-implantation and decreased together with RXFP2 at prepartum luteolysis. The endometrial levels of both receptors did not vary greatly, but myometrial RXFP2 decreased from mid-gestation to prepartum luteolysis. Antigestagen treatment resulted in suppression of RLN in UtPl and decreased RXFP1 and RXFP2 in the uterus. The placental RLN was localized mainly in the cytotrophoblast. Additionally, RXFP1 stained strongly in placental endothelial cells while RXFP2 was found mainly in maternal decidual cells. Uterine staining for all targets was found in epithelial cellular constituents and in myometrium. Finally, besides its endocrine functions, RLN seems to be involved in auto-/paracrine regulation of utero-placental functions in dogs in a time-dependent manner. New insights into feto-maternal communication was provided, in particular regarding the localization of RXFP2 in the maternal decidual cells, implying functional roles of RLN during the decidualization process.

Histomorphometrics and quantitative unbiased stereology in canine uteri treated with medroxyprogesterone acetate

This article describes the effects of MPA use on the canine uterus using stereological methods. Entire reproductive tracts were removed from normal healthy canine bitches (Canis lupus familiaris) and grouped as: nulliparous (n = 11), multiparous (n = 11) and MPA-treated (n = 11; nulliparous; two treatments; 5 mg/kg). 1 cm samples were cut from the corpus, horn and uterine tube and fixed in 10% formaldehyde. Sections of each were mounted on slides and stained with hematoxylin-eosin. We assessed the fraction area for components of endometrium and myometrium and V_V (volume density) and S_V (surface density) of the gland and stroma using the M₃₆ test system provided by the STEPanizer Stereological Tool. No gross histological differences were observed between study groups in the uterine tube, uterine corpus and horn. The wall of the uterine corpus and horn in MPA-treated bitches was characterized as being thicker than in the other groups. A cross-section of the uterine corpus revealed no differences between components of uterine wall in the corpus and horn; however, differences were observed in the volume density [V_V; %] in variables such as: V_{V[str.vasc/uterus]} (nulliparous vs. multiparous; p = 0.0019) and V_{V[str.supravasc/uterus]} (multiparous vs. nulliparous and MPA; p = 0.0035). In the endometrial gland, differences were detected in S_{V[gland/endom]} (multiparous vs. MPA, p = 0.0442). In the uterine horn, differences were only observed in the variable V_{V[lumen.gland/endom]} (multiparous vs. MPA; p = 0.0019). This study shows quantitative changes in the architecture of the endometrium and myometrium in all the uterine segments, mainly morphological endometrial gland changes of the uterine corpus, increasing the surface area per unit of volume; however, these changes usually do not differ quantitatively from those observed in the uterus of multiparous bitches.

Changes in serum progesterone concentrations in Bernese mountain dogs and Cavalier King Charles Spaniels during pregnancy

Progesterone (P4) concentrations during canine pregnancy follow a specific pattern. Although the general pattern is similar, it is likely that breed-specific differences exist. Detailed knowledge about the physiological range of P4 concentrations may be helpful in cases of suspected hypoluteoidism. The aim of this study was to investigate P4 changes during pregnancy in a small and a large breed, to obtain reference values for specific intervals during pregnancy and to test for breed- or body weight-specific differences. We studied P4 concentrations in pregnancies from healthy Bernese mountain dogs (BMDs, n = 6) and Cavalier King Charles Spaniels (CKCSs, n = 6) with a normal reproductive history. Blood samples for P4 were taken to determine the day of ovulation and after confirmation of pregnancy in regular intervals from Days 23 to 29 to Days 60 to 64. Bernese mountain dogs delivered 6.2 ± 2.6 puppies (range: 3-9) 63.4 ± 1.5 (range: 61-65) days after ovulation (excluding data from one BMD with elective c-section) and CKCS delivered 3.3 ± 1.9 puppies (range: 1-5) 63.5 ± 1.1 (range: 62-65) days after ovulation. In general, the P4 concentrations of individual dogs continuously decreased from the first to the last sampling during pregnancy. Respective mean concentrations were Days 23 to 29: 19.2 ± 4.3/22.2 ± 3.9 ng/mL (BMD/CKCS), Days 30 to 34: 15.6 ± 2.3/17.7 ± 5.8 ng/mL, Days 35 to 39: 12.5 ± 2.8/14.1 ± 3.4 ng/mL, Days 40 to 44: 8.9 ± 1.4/11.8 ± 3.7 ng/mL, Days 45 to 49: 7.7 ± 1.6/8.9 ± 1.9 ng/mL, Days 50 to 54: 6.0 ± 1.3/8.7 ± 7.1 ng/mL, Days 55 to 59: 4.7 ± 1.2/5.3 ± 2.8 ng/mL, and Days 60 to 64: 3.69 ± 1.86/2.62 ± 0.42 ng/mL. ANOVA indicated significant differences over time within each breed when considered individually (P < 0.0001 each), but not between breeds although mean P4 was slightly lower in BMD until Days 55 to 59. The present data clearly confirm the previously described P4 pattern during canine pregnancy with highest P4 concentrations obtained in the first interval (Days 23-29) and a subsequent decrease of P4. The lack of a significant rapid prepartal P4 drop might be related to methodological issues (time of last collection in regards to parturition). Other than expected, we failed to proof significant differences in P4 between CKCS and BMD. Further studies are required to confirm the results on a larger population of both breeds, but also other large-sized breeds to test for the hypothesis if BMD might have lower P4 concentrations and smaller litter size compared to other large breeds with larger litter size.

Relaxin: a hormonal aid to diagnose pregnancy status in wild mammalian species

In the beginning of 1960s, seminal studies characterizing circulating concentrations of immunoreactive relaxin in companion dogs and evaluating the differences in concentrations among pregnant, nonpregnant, and pseudopregnant bitches indicated the potential for relaxin to be applied clinically as a diagnostic aid to detect pregnancy status in wild animal species. A brief historical overview of the nature of relaxin and early work to develop and validate immunologic methods to analyze relaxin in the blood of rodents and pigs is initially discussed, which is followed by a summary of the development and validation of relaxin immunoassays to diagnose pregnancy in companion dogs and cats. Thereafter, observation of the pregnancy-specific increase in circulating concentrations of relaxin in laboratory, companion, and farm animal species leads to discussion on the application of radioimmunoassays, enzyme immunoassays, and a rapid immunomigration assay to diagnose pregnancy in wild terrestrial (e.g., wolves, lions, elephants, rhinoceros, panda) and marine (e.g., seals, dolphins) mammal species. A reference table is included with a comprehensive list of numerous species and essential reagents that have been used in various in-house and commercial immunoassays to successfully analyze relaxin quantitatively and qualitatively in blood (serum or plasma) and to some extent in urine. Although the detection of relaxin concentrations has the potential to aid in the diagnosis of pregnancy in many wild animal species, there are challenges in other species. Future efforts should focus on validation of nonradiolabeled relaxin immunoassays for broader application among species and improving techniques (e.g., extraction, purification) to analyze relaxin in samples other than blood (e.g., urine, feces, saliva, blow, skin, blubber) that can be collected in a less-invasive or -stressful manner and processed accordingly for basic and applied purposes, especially with application toward conservation of threatened or endangered species.

Does oral administration of the amino acid tyrosine affect oestradiol-17β concentration and sexual behaviour in the bitch?

The oral administration of the amino acid, tyrosine, has been for years recommended in order to improve fertility, especially to improve copulation behaviour in female dogs. However, evidence is comparatively poor. The objective of our study was to determine whether oral administration of tyrosine has an effect on oestradiol-17β concentrations and the oestrous behaviour in the bitch. Fifty bitches were randomly allocated to one of two treatment groups in which each dog received 100mg/kg/day of either tyrosine or milk sugar orally between Day 3 and Day 9 of heat. Every two to three days, a gynaecological examination was performed and blood samples were taken to determine oestradiol-17β and progesterone concentrations. The day of ovulation was estimated by clinical findings, and according to the specifications of the laboratory, once progesterone values exceeded 12.7nmol/l. The observed copulation behaviour was not different between the groups. No differences in volume and visual nature of vaginal discharge were observed. At the day of ovulation, mean oestradiol-17β concentration in the treated group was 163.4pmol/l and 162.2pmol/l in the placebo group, respectively. In conclusion, feeding tyrosine to female dogs between Day 3 and Day 9 of heat did not alter visual signs of heat or copulation behaviour, and did not alter oestradiol-17β concentration.

Reproductive cycles of the domestic bitch

Domestic dogs are monoestrous, typically non-seasonal, polytocous, spontaneous ovulators and have a spontaneous luteal phase slightly longer (by approx 5 day) than the 64±1day luteal phases of a 65±1day pregnancy, a phase followed by an obligate anestrus before the next 2-3 week "heat" (proestrus-estrus). The resulting inter-estrus intervals of 5-12 months are variable among bitches, commonly 6-7 months, and range from highly variable to regular (to perhaps within±5-10 day of sequential 7 month cycle, for instance) within bitches, and across studies and do not vary significantly between pregnant and non-pregnant cycles. Hormone levels reported are those observed in this laboratory using previously reported assays and canine gonadotropin standards unless stated otherwise. Endocrine sequences for dog cycles are not unlike those of many other mammals, including selection of ovulatory follicles by increased LH pulsatility, the occurrence of estrus behavior and LH surge during a decline in the estrogen: progestin ratio, a pronounced preovulatory luteinization as in humans and rodents, and luteotrophic roles for both LH and prolactin. Non-pregnant bitches have a spontaneously prolonged luteal phase, often longer and with a more protracted decline in serum progesterone than in pregnancy as there is no uterine luteolytic mechanism. The obligate anestrus of 8-40 weeks is terminated by poorly understood interactions of environment (e.g. pheromones, possibly photoperiod) and a potential endogenous circannual cycle in sensitivities of hypothalamic dopaminergic, serotonergic and/or opioid pathways.

Influence of progesterone withdrawal on pregnancy-related parameters during post-implantation early pregnancy loss

Pharmacologically-induced luteolysis or treatment with an antiprogestin in early post-implantation pregnancy in dogs results in asynchronous death and resorption of conceptuses, indicating variable rates of response of individual conceptuses towards progesterone deficiency. This variability also seems to occur in bitches showing pregnancy failure in response to spontaneous luteal deficiency. In a total of 10 beagle pregnancies (two consecutive pregnancies of five bitches), abortifacient treatments beginning on day 24 after ovulation (ov) involved either administration of a progestin antagonist (total of six pregnancies, in three bitches) or a luteolytic regimen of prostaglandin F(2alpha)-analogue together with a dopamine agonist (total of four pregnancies, in two bitches). The outcomes were evaluated in relation to four control pregnancies in two bitches by assay of serum progesterone, prolactin and relaxin at selected time points or within selected time periods, by ultrasound of conceptuses including measurement of uterine blood flow, and parameters of the blood fibrinolytic system including plasma fibrinogen and plasminogen. The process of embryonic death and conceptus resorption was variable in onset and duration both in bitches that received the progesterone antagonist aglepristone (AGLE) and in those under the luteolytic treatment (cloprostenol combined with cabergoline). Pregnancy termination (death of all embryos or foetuses, respectively) occurred as early as day 29 and as late as day 41 after ov in AGLE-treated bitches, and not earlier than day 37 after ov in luteolytic-treatment bitches. Impending embryonic death was not predicted by changes in relaxin concentration, parameters of the fibrinolytic system, or in the perfusion of small uteroplacental vessels.

Endocrinologic control of normal canine ovarian function

In dogs, the termination of the 3-10-month obligate anoestrus involves selection of a cohort of LH-sensitive follicles, presumably from a wave of dominant small antral follicles that would otherwise undergo atresia. The number and size of such follicles appears to increase, especially during the last 50 days of anoestrus when the already elevated concentrations of FSH become further elevated. The final selection and eventual terminal development of these follicles is caused by an increased frequency of high-amplitude LH pulses at the end of anoestrus. Concomitant increases in FSH are typically small or negligible. High concentrations of FSH in anoestrus are likely to be important in maintaining, if not stimulating, overlapping waves of dominant follicles throughout anoestrus, their expression of aromatase activity and basal oestradiol secretion sufficient to suppress LH by negative feedback. An attractive hypothesis is that late anoestrus increases in LH-stimulate synthesis of precursor androgen for already available FSH-dependent aromatase. After 7 or more days of elevated LH, and perhaps 2-5 days of semi-autonomous growth, with maximal oestradiol production reached, follicle capacity to further increase oestradiol becomes limited and excess progesterone becomes increasingly secreted. The pre-ovulatory LH surge and oestrus onset are then triggered - often synchronously and in concert with the terminal maturation of the follicles - by central effects of the large decrease in the oestrogen to progestin ratio. Follicular endocrine and paracrine events during and following the LH surge are likely similar to those reported for other species. The prolonged luteal phase lengths of 55-75 days in non-pregnant bitches bracket the 64 +/- 1 day in pregnancy and represent a genetically programmed luteal cell lifespan approximating gestation length as occurs in the luteal phase of hysterectomized animals of most polyoestrous artiodactyls and rodents. The 30-40-day slow regression after day 20 to 30 involves periodic cell death, diminution in cell size, low levels of apoptosis and minimal or modest involvement of endogenous prostaglandin F (PGF) production. The canine corpus luteum (CL) is dependent on both LH and prolactin as stimulating luteotrophins by day 15, and as required luteotrophins by days 20-25, if not earlier. Thereafter, both luteotrophins likely have cellular mechanisms of action similar to those reported for other species. Progesterone secretion during pregnancy is greatly enhanced by characteristic, and probably relaxin-stimulated, increases in prolactin concentration starting at or after day 25, and persisting to term. Near term, foetoplacental maturation results in the placental release of large, luteolytic amounts of PGF for 1-2 days pre-partum. Pre-partum luteolysis, like that induced by exogenous prostaglandin, likely involves a cascade enhanced by the removal of progesterone inhibition of PGF release and some degree of intra-luteal PGF synthesis. That a likely twofold or greater increase in progesterone production by the CL of pregnancy does not result in significantly higher serum progesterone than in non-pregnant metoestrus relates to several biological changes, including a large increase in plasma volume of distribution, increased metabolism of progesterone by increased uterine, placental and mammary masses and increased liver clearance and excretion of progesterone and progesterone metabolite. Anoestrus length and ovarian cycle intervals, variable within and among bitches, are likely affected by neuroendocrine components of an endogenous circannual cycle, albeit only photo-entrained in the Basenji breed. This may be modified by the prior luteal phase, exposure to oestrus female pheromones and as yet unknown mechanisms that likely operate via inhibitory opioidergic and/or stimulatory dopaminergic hypothalamic pathways affecting late anoestrus increases in LH.

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.

High-risk pregnancy and hypoluteoidism in the bitch

High-risk pregnancies are those in which the prevalence of maternal, fetal and/or perinatal morbidity or mortality is likely to be higher than that of the general obstetrical population. Some maternal characteristics associated with risk to maternal, fetal and/or perinatal health are readily identifiable prior to conception, such as advanced maternal age, brachycephalic breed, or a previous history of pregnancy loss. Others, such as gestational diabetes or a singleton litter, are recognized after conception. Early recognition of the problem (i.e. the risk), anticipation of the potential sequelae, and development of an aggressive management scheme are essential for a successful outcome of a high-risk pregnancy. A previous history of pregnancy loss is a high-risk factor for recurrence during subsequent pregnancies. Infection is a common cause. In some instances, recurrent pregnancy loss is associated with low serum concentrations of progesterone. Although the mechanism(s) by which this occurs is not fully understood, the situation has been called hypoluteoidism. Whatever the cause of the risks to pregnancy, the goals of managing high-risk pregnancies are to optimize maternal, fetal and perinatal health, so as to maintain maternal health throughout pregnancy and lactation and maximize the number of healthy pups surviving to weaning age.

Endocrinology of pregnancy in the dog: a review

Pregnancy regulation in the dog is not yet fully elucidated. Since plasma progesterone concentrations are similar in pregnant versus non-pregnant animals, it is a poor reflection on CL function and progesterone metabolism. Increased progesterone secretion by the CL in pregnant animals follows implantation and relaxin secretion by the feto-placental units. Progesterone is absolutely required to maintain pregnancy and no placental sources of progesterone have been identified. Pregnancy can be artificially maintained by progesterone administration. Prolactin secretion appears to be increased in response to the increase in relaxin production and occurs independent of estrogen production by the CL. The respective roles of LH, FSH and prolactin are still unclear, with considerable conflicting evidence among studies. However, it appears that prolactin is absolutely required, whereas LH is either permissive or facilitates CL function during pregnancy. Pre-implantation events are still poorly defined in the bitch, and no embryonic factors have been isolated or purified, preventing early pregnancy diagnosis. Parturition occurs following luteolysis, which results from the release of prostaglandin F(2alpha), which begins 36h prepartum in a process similar to that observed in other species. The role of estrogens at the time of parturition remains undefined.

Canine and feline pregnancy loss due to viral and non-infectious causes: a review

Among the causes for pregnancy loss, viruses and non-infectious factors are among the most important. In both dogs and cats, research and clinical evidence provide proof that there is an increasing incidence of pregnancy loss associated with infectious diseases like herpesvirus, as well as the presence of toxicants or chemicals in the animal's diet and environment. Endocrine causes must be taken into consideration when dealing with pregnancy loss. This review will cover the most recent knowledge regarding viral and non-infectious of pregnancy losses in the dog and cat.

Canine and feline abortion diagnostics

Knowledge of the causes of canine or feline pregnancy loss is limited and the success rate for making a definitive diagnosis is disappointingly low. Although these facts are discouraging, there are some things that can be done to improve success rates. This paper will address limitations and explore ways for improvement. For abortions caused by microbial infections, there are many reasons why it may not possible to identify the agents. "Non-infectious" causes are much more difficult to diagnose, and their relative importance is unknown. These include endocrine failure, underlying endometrial disease, genetic abnormalities, nutritional deficiencies, and toxicosis from drugs or environmental sources. Genetic abnormalities are a major cause of human pregnancy loss, yet we have little specific information about genetic diseases leading to abortion in animals. This paper addresses ways clinicians and diagnosticians can work together to improve diagnostic success. Necropsy techniques for fetal and placental examination and sampling are briefly reviewed. It is hoped that this series of papers will stimulate discussion on the causes and pathogenesis of pregnancy failure, and focus attention on areas where abortion diagnostics can be improved.

Repeated induction of abortion in bitches and the effect on plasma concentrations of relaxin, progesterone and estradiol-17beta

The aim of the present study was to investigate the effects of two medications on two subsequent abortions and plasma hormone concentrations of dogs. For this purpose, two groups of bitches (n=5 each), received the antiprogesterone aglepristone (Alizine) at 10mg/kg body weight on two subsequent days around day 30 after mating. In group II, the antiprolactin cabergoline (Galastop) was additionally administered po at 5 microg/kg body weight until the start of abortion. The plasma concentrations of relaxin, progesterone (P4) and estradiol-17beta (E2) were measured before, during and after each abortion. During the next cycle after the abortion, the same bitches were mated again and in pregnant animals, induction of abortion was performed as before. During the third cycle, pregnant bitches were allowed to whelp. Termination of first pregnancy occurred significantly earlier after the combined treatment (6.8 versus 10.6 days, p<0.05). In both groups and during both abortions, relaxin varied between individuals; however, there was a continuous decrease after the abortions and no significant differences between groups (p>0.05). In one bitch with high relaxin concentrations before treatment (11.6 ng/ml), a cystic endometrial hyperplasia was diagnosed. In the aglepristone only group, P4 concentrations increased significantly after the first application (p<0.05), then decreased continuously until day 45 after the beginning of abortion. In the combined group, there was a continuous decrease until day 45 (p>0.05). At this time, P4 concentrations between 0.47 and 84.9 nmol/l were measured in both groups. The level of E2 over time was not influenced by any medication. We therefore note that the two medications mainly influenced plasma concentrations of P4 in different ways, probably due to specific treatment-hormone interactions. However, all measurements fell within the range considered normal.