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Topic:Progesterone
Progesterone is a steroid hormone produced primarily by the ovaries in mares and plays a significant role in the reproductive system of horses. It is involved in the regulation of the estrous cycle and the maintenance of pregnancy. Progesterone levels fluctuate throughout the reproductive cycle, influencing reproductive behavior and physiology. In veterinary medicine, measuring progesterone levels can aid in diagnosing reproductive conditions and managing breeding programs. This page compiles peer-reviewed research studies and scholarly articles that explore the production, regulation, and clinical applications of progesterone in equine reproductive health.
Successful induction of lactation in a barren Thoroughbred mare: growth of a foal raised on induced lactation and the corresponding maternal hormone profiles. The purpose of this study was to demonstrate that a barren parous Thoroughbred mare with lactation induced by hormonal treatment can be introduced to an orphan foal at the same farm and that the mare can become pregnant after the end of the hormonal treatment. An additional purpose was to investigate the changes in the plasma concentrations of prolactin, estradiol-17β, progesterone, follicle-stimulating hormone, and luteinizing hormone before, during, and after hormonal treatment. The difference in body weight between the adopted foal and the control foals, which were at the same farm and rai...
Premature luteal regression in a pregnant mare and subsequent pregnancy maintenance with the use of oral altrenogest. Premature luteal demise or luteal insufficiency is not well characterised as a cause of pregnancy loss in domestic species, including horses. In this report, a mare inseminated with cooled-transported semen at our facility returned for a routine pregnancy diagnosis at 15 days post ovulation. Ultrasonography per rectum revealed endometrial oedema and the absence of visual indication of a corpus luteum on either ovary. Nonetheless, an embryonic vesicle small for the gestational age was identified. Daily oral altrenogest treatment was implemented immediately. Serum progesterone concentration was ...
The hour of transition into luteolysis in horses and cattle: a species comparison. Hourly blood sampling in both horses and cattle indicate that the transition between the end of preluteolysis and the beginning of luteolysis occurs within 1 h, as manifested by a change in progesterone concentrations. Each species presents a separate temporality enigma on the relationship between pulses of a prostaglandin (PG) F2α metabolite (PGFM) and the hour of the progesterone transition. In horses, relatively small pulses of PGFM occur during preluteolysis (before transition) and at transition. Oxytocin, but not estradiol, increases and decreases concomitantly with the small PGFM pulse ...
Granulosa theca cell tumour in a pregnant mare: concentrations of inhibin and testosterone in serum before and after surgery. A 14-year-old Thoroughbred mare was presented for evaluation of a rapidly enlarging ovary at 73 days gestation. The mare's owner reported behavioural changes in the mare since she returned from stud, notably aggression towards other horses. Results: Transrectal palpation and ultrasonography of the reproductive tract revealed a viable pregnancy, an enlarged, multiloculated right ovary, and a normal-sized left ovary with a corpus luteum present. Concentrations of inhibin and testosterone in serum were 13.8 ng/mL and 1,150 pg/mL, respectively, being markedly higher than reference ranges. Concentr...
Luteogenic and luteotropic effects of eCG during pregnancy in the mare. The role of eCG during pregnancy was evaluated through the study of the temporal relationships between changes in eCG and progesterone concentrations and the formation of supplementary corpora lutea (SCL) in mares impregnated with donkey semen (mule pregnancies) or with horse semen (equine pregnancies). Concentrations of eCG were higher (p<0.01) in equine than in mule pregnancies between weeks 6.5 and 13. Progesterone concentrations were higher in equine than in mule pregnancies between weeks 9 and 17. All animals developed at least one SCL, but more SCL accumulated during equine pregnancie...
Doppler sonography of the uterine and ovarian arteries during a superovulatory program in horses. The aim of the present study was to investigate the effects of a gonadotropin treatment to induce superovulation on ovarian and uterine blood flow and its relationship with steroid hormone levels and ovarian response in mares, using color Doppler sonography. Each of six mares were examined sonographically in five cycles for 3 d (t1 to t3) during the follicular development phase (FDP) beginning at a follicle size of ≥ 22 mm, and for 4 d (D-4 to D-1; D0 = Ovulation) in the preovulatory phase (POP). After each examination, total estrogens (E(tot)) and progesterone (P(4)) levels were determined ...
The end of the tour de force of the corpus luteum in mares. Recent findings on the luteolytic process in mares are reviewed and differences from other farm species are noted. It is well known that the luteolysin, PGF2α (PGF), is secreted from the endometrium in the absence of pregnancy in farm animal species. But PGF is a potent chemical and safeguards have evolved so that only the corpus luteum (CL) is affected. The safeguards include a short PGF half-life and secretion in two or three pulses per day. In mares, endogenous PGF travels from the uterus to the CL through the systemic circulation, but the luteal-cell membranes are highly efficient in capt...
Effect of progesterone on the in vitro response of peripheral blood mononuclear cells stimulated by Escherichia coli in mares. Escherichia coli(E. coli) isolated from the uterus of a Thoroughbred mare with bacterial endometritis was used to evaluate the effect of progesterone (P(4)) on the immune response of mares. Peripheral blood mononuclear cells (PBMCs) were collected from 10 nonpregnant clinically healthy adult mares (range, 4-12 years) during diestrus, four Thoroughbreds and six Hokkaido native horses. Cell proliferation and expression of cytokine mRNA, including interferon (IFN)-γ, tumor necrosis factor (TNF)-α and interleukin (IL)-10, of PBMCs stimulated with E. coli and P(4) were examined in vitro. P(4) was...
The reproductive performance of Thoroughbred mares treated with intravaginal progesterone at the start of the breeding season. The objective of this study was to investigate the effects of intravaginal progesterone on the reproductive performance of transitional Thoroughbred mares on commercial stud farms. Two hundred twenty-seven (227) non-lactating transitional Thoroughbred mares aged between 4 and 18 y (mean 9.4 ± 3.2 y) located on three stud farms in the Waikato region of New Zealand were used in the study performed during four consecutive breeding seasons (2007-10). Mares were age-matched in pairs and either treated with an intravaginal progesterone releasing device (Cue-Mare, 1.72 g progesterone, 10% w/w) for u...
Immunohistochemical localisation of progesterone and oestrogen receptors at the placental interface in mares during early pregnancy. Previous reports documenting progesterone receptors (PR) and oestrogen receptors (ER) in the endometrium of early pregnant mares included specimens only up to Day 20 post ovulation. This study aimed to localise PR and ERα on equine feto-maternal tissues between Days 20 and 68 to encompass the period around fixation of the conceptus, development of the endometrial cups and attachment and initial interdigitation of the allantochorion. During early pregnancy mares had the same pattern of PR in the endometrium as that reported for other mammals; namely, a loss of PR from the endometrial epithelia...
Hormone concentration changes temporally associated with the hour of transition from preluteolysis to luteolysis in mares. The temporal associations of cortisol, estradiol-17β, and oxytocin with pulses of PGFM at the common hour of transition between preluteolysis and luteolysis was studied in plasma from hourly blood samples in mares (n=8). The transitional hour was determined from progesterone concentrations and occurred between 2PM and 2AM in all mares. Pulses of PGFM were grouped into those occurring at the last pulse of preluteolysis (preluteolytic pulse), at the hour of transition (transitional), and during luteolysis (luteolytic). The preluteolytic PGFM pulse (45±16pg/ml at peak) and transitional pulse (4...
Distribution of mast cells in vaginal, cervical and uterine tissue of non-pregnant mares: investigations on correlations with ovarian steroids. Mast cells constitute part of the cellular immune system of the genital tract. They play a potential role in cervical remodelling during parturition and are subject to the influence of ovarian steroids. In this study, the influence of oestradiol-17β and progesterone on the distribution of mast cells in equine vaginal, cervical and uterine tissue was evaluated. Genital tracts were retrieved from healthy mares at a local slaughterhouse. The cervix was divided along the longitudinal axis into five equivalent regions from cranial to caudal (R1 to R5). Toluidine blue staining was used for the dete...
Concentrations of circulating hormones during the interval between pulses of a PGF2α metabolite in mares and heifers. The temporal relationship of several hormones to a metabolite of prostaglandin F2α (PGFM) was studied in mares and heifers from the beginning of the first PGFM pulse during luteolysis to the end of the second pulse. Mares (n=7) were selected with a 9-h interval between the peaks of the two pulses. In mares, estradiol-17β (estradiol) increased (P<0.05) within each PGFM pulse and plateaued for a mean of 6h between the pulses, resulting in a stepwise estradiol increase. Progesterone decreased linearly (P<0.0001) throughout the intra-pulse and inter-pulse intervals of PGFM. In heifers (n=6...
Progesterone production in mares and echographic evaluation of the corpora lutea formed after follicular aspiration. Ultrasound-guided follicular aspiration was performed in 26 Criollo crossbred mares, followed by the evaluation of ultrasonographic images of the Corpus luteum (CL) that was formed after puncture of follicles of different diameters (Group 25-29 mm; Group 30-35 mm and Group >35 mm). Serum progesterone (P(4) ) concentrations were measured to determine CL function. The size of the CL was measured and the CL was classified based on the following echoscore: 1- anechoic tissue; 2- poorly defined luteal structure with low echogenicity; 3- echogenicity analogous to a luteal structure. The proport...
Morpho-functional studies regarding the fertility prognosis of mares suffering from equine endometrosis. The aim of the present study was to characterize the morpho-functional features of endometrosis in barren and foaling mares, using both conventional histopathological and immunohistochemical methods. Endometrial biopsy samples were collected during the physiological breeding season from 159 estrous, clinically healthy mares (mean age 12 years), and the quality and degree of endometrosis was histomorphologically defined. The mares were bred and those that foaled were put in the foaling group whereas those that did not foal were placed in the barren group. Foaling mares were then compared with b...
Administration of a gonadotropin-releasing hormone antagonist to mares at different times during the luteal phase of the estrous cycle. The GnRH antagonist cetrorelix was given during the early (Days 1-5), mid (Days 6-10 or 5-12) or for the entire (Days 1-16) luteal phase of mares to inhibit the secretion of FSH and LH (Day 0=ovulation). Frequent blood sampling from Day 6 to Day 14 was used to determine the precise time-course of the suppression (cetrorelix given Days 6-10). Cetrorelix treatment caused a decrease in FSH and LH concentrations by 8 and 16 h, respectively, and an obliteration of the response to exogenous GnRH given 24h after treatment onset. Treatment never suppressed gonadotropin concentrations to undetectable l...
Relationship between progesterone, oestrone sulphate and cortisol and the components of renin angiotensin aldosterone system in Spanish purebred broodmares during pregnancy. The coordinated interaction of the components of the renin angiotensin aldosterone system (RAAS) with reproductive hormones such as progesterone, oestrogens and cortisol during pregnancy has been widely reported to play a vital role in foetal and placental development in various species, significantly influencing the proper achievement of pregnancy and foetal viability at birth. These interactions have not yet been clarified in mares. Thus, the purpose of the present research was to analyse the relationship between cortisol (CORT), progesterone (P4) and oestrone sulphate (OESTRONE), and the co...
The effect of treatment with flunixin meglumine at different times relative to hCG administration on ovulation failure and luteal function in mares. Flunixin meglumine (FM), a prostaglandin synthetase inhibitor, causes ovulatory failure in the mare. However, the effect of the FM treatment relative to the time of hCG administration on the ovulation failure has not been determined nor has its effect on the luteal function of treated mares. Estrous mares with a follicle ≥32 mm (range of 32-38 mm) were treated with 1.7 mg/kg b.w. of FM iv at zero, 12, 24 and 36 h (n=6), at 24 and 36 h (n=6), at 28 and 36 h (n=6), at 24h (n=6) or at 30 h (n=6) after treatment with 1500 IU hCG. One group received no FM (control, n=6). Progesterone concentratio...
Luteolysis and associated interrelationships among circulating PGF2α, progesterone, LH, and estradiol in mares. The changing concentrations and temporal relationships among a PGF2α metabolite (PGFM), progesterone (P(4)), LH, and estradiol-17β (E(2)) before, during, and after luteolysis were studied in 10 mares. Blood samples were collected every hour for ≥4 d beginning on day 12 after ovulation. The luteolytic period extended from a decrease in P(4) at a common transitional hour (Hour 0) at the end of preluteolysis and beginning of luteolysis to a defined ending when P(4) reached 1 ng/mL. The length of luteolysis was 22.9 ± 0.9 h, contrasting with 2 d in published P(4) profiles from sampling every ...
The effect of systemic administration of cloprostenol on ovulation in mares treated with a prostaglandin synthetase inhibitor. Prostaglandins (PGs) are essential to trigger the cascade of events that degrade the extracellular matrix of follicles leading to follicular rupture and ovulation. In mares, systemic administration of flunixin meglumine (FM), a PG synthetase inhibitor, blocks ovulation by inducing luteinized unruptured follicles (LUF). In the rat, the administration of PGF(2α) (PGF) and PGE restored ovulation in indomethacin treated animals. The mares were treated with FM 0, 12, 24 and 36 h after human chorionic gonadotrophin (hCG) administration to induce experimentally LUF (n = 15) or were left untreated (c...
Follicle and systemic hormone interrelationships during induction of luteinized unruptured follicles with a prostaglandin inhibitor in mares. The objective was to determine differences in follicle and reproductive hormone characteristics in mares with ovulatory and flunixin meglumine (FM)-induced anovulatory cycles. Estrous mares were given 1500 IU hCG when the follicle was ≥ 32 mm (0 h). In Experiment 1, control mares (n = 7) were not treated further. The remaining mares (n = 11) were given 1.7 mg/kg FM i.v. twice daily, from 0 to 36 h after hCG treatment. Blood samples and ultrasonographic examinations were performed every 12 h. All control mares ovulated normally between 36 and 48 h. In contrast, eight of 11 FM mares did not ov...
Expression of wingless type (WNT) genes and their antagonists at mRNA levels in equine endometrium during the estrous cycle and early pregnancy. WNT signaling pathway plays important roles in reproductive events. Aims were to (1) determine presence of WNT genes and their antagonists in equine endometrium; and (2) to evaluate their expression profiles during early pregnancy. Endometrial biopsies were obtained from mares on day of ovulation (d0, n=4) and on days of 14 (P14, n=4), 18 (P18, n=4), 22 (P22, n=4) of early pregnancy. Biopsies were also collected from cyclic mares during late diestrus (LD, on day of 13.5-14, n=4) and after luteolysis in estrus phase (AL, on day of 17.5-18, n=4) of the cycle. PCR was used to detect expression of...
Expression of functional melatonin MT(1) receptors in equine luteal cells: in vitro effects of melatonin on progesterone secretion. In the present study, we analysed the molecular mechanism(s) by which melatonin directly affects ovarian function in the mare. In Experiment 1, follicles and corpora lutea (CL) were collected from slaughterhouse ovaries and analysed for melatonin (MT(1)) receptor mRNA and protein. In Experiment 2, CL were collected from slaughterhouse ovaries and cultured in Dulbecco's modified Eagle's medium-F12 medium (control medium) supplemented with 50 ng mL(-1) equine chorionic gonadotrophin (eCG), 1 nM-1 μM melatonin, 1 μM forskolin or 1 μM luzindole. Explants were cultured for 3 h in the presence of...
Influences of treatment of early pregnant mares with the progestin altrenogest on embryonic development and gene expression in the endometrium and conceptus. A positive influence of altrenogest treatment on a retarded development of the conceptus around the beginning of placentation in mares older than 8 years could be recently demonstrated. In the present study, effects of altrenogest treatment in early-pregnant mares on conceptus development and expression of endometrial and embryonic genes were investigated. Genes were chosen according to a possible involvement in embryo-maternal interaction and embryonic development in the equine species. Mares were treated with altrenogest (0.044 mg/kg bodyweight) or sunflower oil (placebo) from day 5 to 11 af...
Functions of ectopically transplanted invasive horse trophoblast. The invasive and fully antigenic trophoblast of the chorionic girdle portion of the equine fetal membranes has the capacity to survive and differentiate after transplantation to ectopic sites. The objectives of this study were to determine i) the survival time of ectopically transplanted allogeneic trophoblast cells in non-pregnant recipient mares, ii) whether equine chorionic gonadotropin (eCG) can be delivered systemically by transplanted chorionic girdle cells, and iii) whether eCG delivered by the transplanted cells is biologically active and can suppress behavioral signs associated with e...
Reproductive cycles of horses. Horses are long-day breeders. During the breeding season, cycle length is about 22 days with 5-7 days of oestrus. Gonadotroph cells are localized in the pars distalis as well the pars tuberalis of the pituitary and heterogeneity in the pattern of LH and FSH storage within the gonadotroph population is considered the basis for the differential regulation of gonadotrophin secretion throughout the reproductive cycle. No short and distinct periovulatory LH peak exists in the mare. The equine ovary has an extreme large size and weight. One to two major follicular waves develop per cycle. The preovu...
Supplementation of equine early spring transitional follicles with luteinizing hormone stimulates follicle growth but does not restore steroidogenic activity. This study was conducted to test the hypothesis that supplementation of growing follicles with LH during the early spring transitional period would promote the development of steroidogenically active, dominant follicles with the ability to respond to an ovulatory dose of hCG. Mares during early transition were randomly assigned to receive a subovulatory dose of equine LH (in the form of a purified equine pituitary fraction) or saline (transitional control; n = 7 mares per group) following ablation of all follicles >15 mm. Treatments were administered intravenously every 12 h from the day th...
Serum levels of acute phase proteins: SAA, Hp and progesterone (P4) in mares with early embryonic death. The study involved 46 healthy purebred Arabian mares exhibiting regular oestrous cycles that underwent artificial insemination (AI). Pregnancy was detected ultrasonographically (US) in 40 mares. In 15 mares in foal, early embryonic death (EED) was observed during the pregnancy days 14-21. Blood for determinations of serum acute phase proteins (SAA and Hp) and progesterone (P4) was sampled 12-24 h before ovulation and the first insemination, at 12, 24, 72, 96 h and on day 7, 10, 14, 21, 35 and 55 after ovulation. The results revealed that in 25 mares without EED, the serum levels of P4, SAA and...
Effect of a povidone-iodine intrauterine infusion on progesterone levels and endometrial steroid receptor expression in mares. Intrauterine infusions have been widely used for the treatment of endometritis in the mare. Nevertheless, their consequences on endocrine and endometrial molecular aspects are unknown. We studied the effect of a 1% povidone-iodine solution intrauterine infusion on progesterone levels, endometrial histology and estrogen (ERα) and progesterone (PR) receptor distribution by immunohistochemistry. Methods: Fourteen healthy mares were used in this study. Estruses were synchronized and seven mares were treated with intrauterine infusions at days 0 and 2 post ovulation of two consecutive estrous cycl...
Intrauterine administration of plant oils inhibits luteolysis in the mare. The maternal recognition of pregnancy (MRP) signal in the mare has not been determined, although oestrogens have been proposed as a potential candidate. Objective: To determine effects of intrauterine administration of oestrogen and various oils on cyclic luteolysis in the mare. Objective: Intrauterine oestradiol or fatty acids may suppress luteolysis in the cycling mare when administered during late dioestrus. Methods: A single 1 ml dose of slow-release oestradiol (10 mg/ml) in fractionated coconut oil was infused into the uterine lumen of cycling mares on Days 6, 8, 10, 12 or 14 post ovulati...
