The corpus luteum is a temporary endocrine structure in the ovaries of horses that forms after ovulation. It develops from the remnants of the ovarian follicle and is responsible for producing the hormone progesterone, which is essential for maintaining pregnancy. The formation, function, and regression of the corpus luteum are regulated by complex hormonal interactions, primarily involving luteinizing hormone (LH). Changes in the corpus luteum can influence reproductive cycles and fertility in mares. This page compiles peer-reviewed research studies and scholarly articles that explore the formation, function, and physiological significance of the corpus luteum in equine reproductive health.
Delchiaro SB, Oliveira PVLF, Júnior RJP, Gonçalves GD, Morotti F, Seneda MM.Mares (n = 77) were evaluated by antral follicle count (AFC) and selected as embryo recipients. Cyclic recipients received embryos between days 4-6 after ovulation. The acyclic recipients received an intramuscular (i.m.) protocol with 5mg of estradiol benzoate (EB) on the day of donor ovulation (D0; D-4 recipient), 3mg of EB on the following day (D1; D-3 recipient), and 3mg of EB (D2; D-2 recipient). Furthermore, 1500mg of progesterone (P4) i.m. given on D0 of the recipient (D4 donor) followed by 1500mg of P4 on the day of ET (D4-6 recipient). On the ET day, the AFC and animals' weight, body c...
Morelli KG, Lourenço GG, Marangon VR, Feltrin IR, Imura Oshiro TS, Rodrigues da Silva IV, Pugliesi G.We aimed to evaluate the impact of corpus luteum (CL) and uterine characteristics accessed by B-mode and Color-Doppler ultrasonography in recipient mares at the time of embryo transfer (ET) on pregnancy outcomes. Recipient mares (n = 110), between days 3-9 after spontaneous ovulation, received a fresh embryo. Immediately before ET, the reproductive system was assessed by transrectal palpation for the following parameters: uterine tone (0-3), CL echogenicity (0-6), CL type (homogeneous, trabecular or anechoic center), luteal area (cm2), uterine echogenicity (0-3), uterine edema (0-3), luteal ...
The present experiment aimed at determining whether the timing of the maternal recognition of pregnancy (MRP) was specific to individual mares by determining when luteostasis, a failure to return to oestrus, reliably occurred in individuals following embryo reduction. Singleton (n = 150) and synchronous twin pregnancies (n = 9) were reduced in 10 individuals (5-29 reductions/mare) at pre-determined time points within days 10 (n = 20), 11 (n = 65), 12 (n = 47), 13 (n = 12) or 14 (n = 15) of pregnancy. Prior to embryo reduction, the vesicle diameter was measured in 71% (106/150) of the singleton...
Bigler NA, Gross JJ, Baumrucker CR, Bruckmaier RM.This review discusses endocrine and functional changes during the transition from late gestation to lactation that are related to the production of colostrum in different mammalian species. Species covered in this article include ungulate species (cattle, sheep, goats, pigs, horses), rodents (rat, mouse), rabbits, and carnivores (cats, dogs), as well as humans. An immediate availability of high quality colostrum for the newborn after birth is crucial in species where a transfer of immunoglobulins (Ig) does not or only partially occur via the placenta during pregnancy. Declining activity of ges...
Ginther OJ.Examples of research discoveries and first reports on mare reproduction by the O.J. Ginther team are (1) determined daily circulating concentrations of four hormones during the estrous cycle, (2) showed that mares can be induced to ovulate and superovulate by hormone treatment during both ovulatory and anovulatory seasons, (3) demonstrated that prostaglandin F2α was the luteolysin in mares, (4) described the mare's elaborate hormonal and biochemical mechanism for selecting the ovulatory follicle from a pool of like follicles, (5) developed the method for diagnosing fetal sex by Day 60 using l...
Diel de Amorim M, Dong L, Byron M, Foster RA, Klein C, Saleh M, Saleh T, Card C.Oxytocin is a hormone with functions in: reproduction, maternal bonding, milk ejection, and feeding/social behavior, and is reported to be present in a variety of tissues. Our goal is to characterize oxytocin and leucyl and cystinyl aminopeptidase (LNPEP/oxytocinase), a key regulator of oxytocin in mares. We measured serum and tissue LNPEP by ELISA from ovulation (D0) until D21-22 in non-pregnant (n = 5) and pregnant mares (n = 6); and in periparturient and postpartum mares (n = 18). Placenta (n = 7) and homogenized tissue of diestrus mares (n = 6) were evaluated using prot...
Silva ESM, Newcombe JR, Cuervo-Arango J.Oestrogens treatment is often used to induce oestrus behaviour in anoestrous mares to aid in the collection of stallion semen and as recipient mares to receive embryos when combined with progesterone. However, there are no studies to describe the effect of dose and individual mare on the intensity and duration of the response, in both anoestrous and cyclic mares. In Experiment 1, 13 anoestrous mares were treated with one of five doses of oestradiol benzoate (OB) (1, 1.5, 2, 3 and 4 mg) per mare in five consecutive treatment periods (n = 65), to determine the response in terms of endometrial oe...
Magalhaes HB, Canisso IF, Dell-Aqua JA.This study aimed to determine the associations between B-mode and Power-doppler ultrasonography and ovarian steroids of the periovulatory follicle and respective corpus luteum (CL) during luteogenesis and luteolysis in jennies. Twenty-four periovulatory follicles/estrus of correspondent one inter-ovulatory interval (n = 12 jennies) were assessed in the study. B-mode ultrasonography and teasing were carried out once day until the detection of a periovulatory follicle (≥28 mm, uterine edema, and signs of estrus). Thereafter, jennies were monitored at 4-hour-intervals by B-mode and Power-dopp...
Grabowska A, Kozdrowski R.Progesterone plays a crucial role in the maintenance of pregnancy from conception to about 100-120 days of gestation when placenta becomes the main source of gestagens. The aim of the study was to test progesterone concentration 14 days after ovulation in pregnant mares and relate it to peak estral endometrial edema and the presence of intrauterine fluid (IUF) after artificial insemination (AI), the number of treatments against IUF, and the time from AI to the day when the uterus was found free of fluid. Results: Mares were divided into two groups: group A (n = 13; age 10.8 ± 4.5 y...
Okada CTC, Kaps M, Reichart U, Walter I, Gautier C, Aurich J, Aurich C.While detrimental effects of reduced plasma progesterone concentration in the early luteal phase on conceptus development in horses have recently been demonstrated, there is no information on associated effects on the endometrium, allantochorion (AC), and chorionic girdle (CG) in this species. We hypothesised that reduced early postovulatory progesterone concentration in pregnant horses is detrimental to endometrial function and development of the embryonic membranes and is an underlying cause of delayed conceptus development. After insemination and ovulation, mares (n = 11) were assigned to...
Aragunde Vieytes R, Viñoles Gil C, Gastal GDA, Cavestany D.In order to assess the effect of equine chorionic gonadotropin (eCG) administered on Day 5 or 7 of a fixed-time artificial insemination protocol (FTAI) in anestrous suckled beef cows, two experiments were performed to determine the following endpoints: Experiment 1 (n = 22), preovulatory follicle (POF) diameter, ovulation time, corpus luteum (CL) area, estradiol (E2) and progesterone (P4) concentrations; and Experiment 2 (n = 676), a field trial to evaluate conception rate using the same experimental design. In both experiments, a synchronization protocol using estradiol benzoate (EB) (Day...
Duval LH, Rechsteiner SMF, Gastal GDA, Gastal MO, Mattos RC, Gastal EL.After having been brought to America 400 years ago, the Criollo horse reproduced freely for centuries in the southern part of the American continent. Roughness, resistance, and endurance are typical characteristics of this breed of horses. Although the natural selection that occurred over the centuries may have positively influenced the fertility and longevity of this breed, information regarding ovarian function and other reproductive aspects of Criollo breed mares under natural or controlled management conditions is scarce. The objectives of the present study were to (1) characterize the fol...
Diel de Amorim M, Bramer SA, Rajamanickam GD, Klein C, Card C.Our understanding of the temporal changes in endometrial and luteal gene transcripts related to the actions of oxytocin and prostaglandin during early equine pregnancy is incomplete. Additionally, the role of oxytocinase, also known as Leucyl-cystinyl aminopeptidase (LNPEP), during early pregnancy in mares has not been previously investigated. Luteal and endometrial biopsies were obtained on Day (D)8, D10, D12 and D15 post-ovulation in pregnant (PREG) and diestrus (DIEST) mares for real-time qPCR. Differences in endometrial gene expression occurred over time in: SLC2A4, SLC2A1, PTGES, OXTR and...
Ortega-Ferrusola C, Gómez-Arrones V, Martín-Cano FE, Gil MC, Peña FJ, Gaitskell-Phillips G, Da Silva-Álvarez E.Ultrasound technology has led to new lines of research in equine reproduction, and it has helped to greatly improve clinical diagnosis and reproductive outcomes in equine practice. This review aims to discuss the potential clinical uses and new approaches of ultrasonography in equine reproduction. Doppler modalities are usually used to evaluate the vascularization of the follicles, corpus luteum (CL), and the uterus in the mare for diagnostic purposes. Inclusion of Doppler ultrasound in artificial insemination and embryo transfer programs could improve the reproductive outcome of these techniq...
Colombo I, Podico G, Rudolf-Vegas A, Bauersachs S, Canisso IF.Progesterone is pivotal to maintain pregnancy in the first trimester and low concentration ( .05). Multiple ovulations were associated with greater progesterone concentration and luteal tissue area (P = .0001). There was a moderate positive association between the number of ovulations and luteal tissue area (r = 0.54; P = .0001). The lack of change in the progesterone concentration and luteal tissue area between bred and non-bred mares suggests that horse seminal plasma does not affect luteal function in mares. As all mares had progesterone above 4 ng/mL after 5-days post-ovulation; it i...
Fanelli D, Beltramo M, Conte G, Cerretini B, Lomet D, Rota A, Aucagne V, Camillo F, Panzani D.Kisspeptins (KPs) are the most potent stimulating neurotransmitters of GnRH release, and consequently KP administration triggers LH and/or FSH release. In small ruminants, KP or its analogs induced an LH surge followed by ovulation in both cyclic and acyclic animals, while in the mare KP only increased LH plasma levels but failed to induce ovulation. This study in jennies compares the endocrinological effects, ovulatory and pregnancy rates of the KP analog C6 and the GnRH analog buserelin acetate. The ovarian activity of nine Amiata jennies was monitored daily by transrectal ultrasound for thr...
Aurich C, Kaps M.The behaviour of mares is often detrimental to their performance resulting in frequent demand for methods to suppress gonadal function. In addition, prevention of unintended reproduction especially in feral horse populations may require methods for suppression of gonadal function. Surgical ovariectomy is a safe method but not an acceptable approach in feral mares and undesired in mares where future breeding is considered. There are different approaches for artificial prolongation of the luteal phase resulting in transient inhibition of oestrus and ovulation. Among those, treatment with natural...
Spencer KM, Podico G, Megahed AA, Jones KL, Bittar JHJ, Canisso IF.This study aimed to assess the ovulatory response of deslorelin acetate during the fall and the response to PGF2α 8 d post-ovulation. One hundred estrous cycles from 22 mares kept in 40° latitude were evaluated. Mares were checked by transrectal ultrasonography until a preovulatory follicle was detected and ovulation induced with deslorelin acetate. Ovulation was confirmed by ultrasonography performed at 24, 36 h post-induction and then repeated at 2-h intervals post-induction. Serum progesterone concentrations and luteal tissue area were determined daily to assess CL function. A dose of P...
Piotrowska-Tomala KK, Jonczyk AW, Szóstek-Mioduchowska AZ, Żebrowska E, Ferreira-Dias G, Skarzynski DJ.We examined the effect of prostaglandin (PG) E on the secretory function of equine corpus luteum (CL), according to the application site: intra-CL injection vs. an intrauterine (intra-U) administration. Moreover, the effect of intra-CL injection vs. intra-U administration of both luteotropic factors: PGE and human chorionic gonadotropin (hCG) as a positive control, on CL function was additionally compared. Mares were assigned to the groups ( = 6 per group): (1) an intra-CL saline injection (control); (2) an intra-CL injection of PGE (5 mg/ml); (3) an intra-CL injection of hCG (1,500 IU/ml); (4...
Domingues RR, Ginther OJ, Gomez-Leon V, Castro T, Wiltbank MC.In heifers and mares, multiple pulses of prostaglandin F2alpha (PGF) are generally associated with complete luteal regression. Although PGF pulses occur before and during luteolysis, little is known about the role of minor PGF pulses during preluteolysis on subsequent luteal and endometrial PGF production that may initiate luteolysis. Heifers (n = 7/group) and mares (n = 6/group) were treated with a single minor dose of PGF (3.0 and 0.5 mg, respectively) during mid-luteal phase (12 and 10 days postovulation respectively). After treatment, a transient decrease in progesterone (P4) con...
Fouché N, Gerber V, Bruckmaier RM, Erni-Wespi B, Zander Y, Vidondo B, Sieme H, Claes A, Kaeser R, Burger D.Anti-Müllerian Hormone (AMH) has been linked to reproductive tract abnormalities in mares and stallions. This study aimed at evaluating AMH as a biomarker for two reproductive conditions in mares. In the first part of this study, plasma AMH was evaluated as an early indicator of the onset of cyclicity in mares in the transitional period from the anovulatory phase during winter anoestrus to the cyclic phase during the breeding season. Ten mares between 8 and 17 years old were included in the experiment which lasted from mid-February until the end of April. Ovarian activity was monitored with u...
Rudolf Vegas A, Podico G, Canisso IF, Bollwein H, Almiñana C, Bauersachs S.During the period of maternal recognition of pregnancy (MRP) in the mare, the embryo needs to signal its presence to the endometrium to prevent regression of the corpus luteum and prepare for establishment of pregnancy. This is achieved by mechanical stimuli and release of various signaling molecules by the equine embryo while migrating through the uterus. We hypothesized that embryo's signals induce changes in the endometrial gene expression in a highly cell type-specific manner. A spatiotemporal transcriptomics approach was applied combining laser capture microdissection and low-input-RNA se...
Hoopes KH, Gradil CM, Vanderwall DK, Mason HM, Sarnecky BA, Davies CJ.There is an urgent need for practical methods of population control (i.e., contraception and/or sterilization) for free-roaming (i.e., "wild" or "feral") horses and burros on Western Public Lands in the United States. The objective of this study was to evaluate the contraceptive efficacy of a novel self-assembling three-part polymer-coated magnetic intrauterine device termed as an intrauterine POD (self-assembling; iUPOD) when there are natural breeding conditions when iUPOD use was managed by veterinary professionals with no prior experience with the device. Six mares were administered an iUP...
Segabinazzi LGTM, Landers M, Kent A, Peterson E, Gilbert R, French H.Due to the limited literature available evaluating doses of Prostaglandin F2α in donkeys, doses for horses have been extrapolated and used as guidelines. This study aimed to assess the efficacy and side effects of four different cloprostenol sodium and dinoprost tromethamine doses to induce luteolysis in jennies. Sixty-three cycles of seven Jennies (nine cycles per jenny) were used in this study. Seven days after ovulation, jennies randomly received one of the treatments in a crossover design as follows: Control, no treatment was administered; C1, 250 µg of cloprostenol sodium (CS, Estrumate...
Gastal EL, Pastorello M, Godoi DB, Gastal MO.This comparative study between postpartum lactating (PP Lactating) and non-postpartum cycling (N-PP Cycling) mares aimed to characterize reproductive patterns, types and frequencies of follicular waves, corpus luteum and endometrial echotexture dynamics, and the influence of season and body condition. Mares from each group were paired considering the day of parturition of a PP Lactating mare. The partum-ovulation interval (POI) and the postpartum interovulatory interval (PPIOI) were evaluated for PP Lactating mares, and 2 IOIs were evaluated for N-PP Cycling mares. The following observations w...
Requena F, Campos MJAPM, Martínez Marín AL, Camacho R, Giráldez-Pérez RM, Agüera EI.In equine reproduction, accurate and timely detection of the moment of ovulation is of great importance. Power Doppler ultrasound technology is a non-invasive method that enables to assess the morpho-echogenic features and blood flow changes during the estral cycle in mares. The objective of the present study was to evaluate the influence of age on ultrasonographic parameters (follicular diameter, follicular blood flow-FBF, corpus luteum (CL) area and corpus luteum blood flow-CLBF) and blood plasma progesterone concentrations in cycling Spanish Purebred mares (15 less than 8 years old and 15 e...
Segabinazzi LGTM, Oba E, Alvarenga MA.Equine practitioners often prescribe the combined use of hCG and GnRH to hasten ovulation due to presumed synergistic effects. Therefore, this study aimed to test whether the combination of hCG and deslorelin acetate to hasten ovulation in mares would show any effect in inducing ovulation more efficiently than when either drug is used by itself, and to verify whether this association would affect progesterone concentrations; corpus luteum (CL) diameter and blood flow; and pregnancy outcome in recipient mares after embryo transfer (ET). Seventeen mares had the ovulation hastened (≥35 mm folli...
Swegen A.Maternal recognition of pregnancy (MRP) is a process by which an early conceptus signals its presence to the maternal system and prevents the lysis of the corpus luteum, thus ensuring a maternal milieu supportive of pregnancy continuation. It is a fundamental aspect of reproductive biology, yet in the horse, the mechanism underlying MRP remains unknown. This review seeks to address some of the controversies surrounding the evidence and theories of MRP in the equine species, such as the idea that the horse does not conform to the MRP paradigm established in other species or that equine MRP invo...
Sales FABM, Azevedo MV, Souza NM, Ferreira-Silva JC, Chaves MS, Junior VR, Rocha JM, Dos Santos Filho JP, Freitas VJF, Oliveira MAL.The aim of this study was to evaluate the correlation between the corpus luteum vascularization with the concentration of progesterone and the fertility of embryo recipient mares. Mangalarga Marchador mares (n = 33) were distributed into groups according to the days (D) after ovulation, as follows: D3 (n = 8), D4 (n = 8), D5 (n = 9), and D6 (n = 8). The evaluations of the corpus luteum, endometrium, and blood collection to quantify the progesterone concentration were carried out on D3, D4, D5, and D6. Among the parameters evaluated, only progesterone concentration on D6 differed from the other...
Okada CTC, Kaps M, Perez Quesada J, Gautier C, Aurich J, Aurich C.Spontaneous prolongation of the luteal phase has been described in horses, but the underlying causes are still unclear. The present study investigated details of gonadotrophin and progestogen secretion in pregnant mares (n = 11) with or without experimentally reduced early postovulatory luteal function. From days 0 to 3 after ovulation, they were treated with the prostaglandin F (PGF) analogue cloprostenol or left untreated. After conceptus collection on day 34, they were assigned to the opposite treatment. Mares were affiliated to the group primary corpus luteum (n = 6) or diestrous corpus lu...
Aurich C.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...
Allen WR.The equine embryo takes 6 days to traverse the oviduct and, when it finally enters the uterus, it remains spherical in shape and moves continually throughout the uterine lumen until day 17 after ovulation to deliver its maternal recognition of pregnancy signal to the entire endometrium. Between day 25 and day 35 after ovulation, the trophoblast cells of a discrete annulate portion of the chorion multiply rapidly and acquire an invasive phenotype and, between day 36 and day 38, migrate deeply into the maternal endometrium to form the equine-unique endometrial protuberances known as endometrial ...
Galvão AM, Ferreira-Dias G, Skarzynski DJ.In adults, physiological angiogenesis is a rare event, with few exceptions as the vasculogenesis needed for tissue growth and function in female reproductive organs. Particularly in the corpus luteum (CL), regulation of angiogenic process seems to be tightly controlled by opposite actions resultant from the balance between pro- and antiangiogenic factors. It is the extremely rapid sequence of events that determines the dramatic changes on vascular and nonvascular structures, qualifying the CL as a great model for angiogenesis studies. Using the mare CL as a model, reports on locally produced c...
Adams GP, Ratto MH.Ovulation in mammals involves pulsatile release of GnRH from the hypothalamus into the hypophyseal portal system with subsequent release of LH from the anterior pituitary into systemic circulation. Elevated circulating concentrations of LH induce a cascade of events within the mature follicle, culminating in follicle rupture and evacuation. The broad classification of species as either spontaneous or induced ovulators is based on the type of stimulus responsible for eliciting GnRH release from the hypothalamus. In spontaneously ovulating species (e.g., human, sheep, cattle, horse, pigs), relea...
Bazer FW, Vallet JL, Roberts RM, Sharp DC, Thatcher WW.Conceptuses produce steroids, prostaglandins, proteins and possibly other unidentified agents which may play a role in the establishment and maintenance of pregnancy. A key event in this process is protection of the corpus luteum (CL) from the luteolytic activity of prostaglandin (PG) F-2 alpha of uterine origin. Oestrogens produced by the pig conceptuses between Days 11 and 16 appear to exert an antiluteolytic effect resulting in the sequestering of PGF-2 alpha within the uterine lumen. Failure of the pregnant uterus to release PGF-2 alpha in an endocrine fashion, therefore, allows for mainte...
Stout TA.The first month of equine pregnancy covers a period of rapid growth and development, during which the single-cell zygote metamorphoses into an embryo with a functional circulation and precursors of many important organs, enclosed within extraembryonic membranes responsible for nutrient uptake and gaseous exchange. After exiting the oviduct, the conceptus must influence uterine physiology to ensure adequate nutrition and preparation for implantation, while continued development results in the chorioallantois superseding the yolk sac as the primary interface for maternal interaction and exchange...
Ginther OJ, Gastal EL, Gastal MO, Utt MD, Beg MA.The temporal relationships between blood flow in the corpus luteum (CL) and circulating progesterone concentrations were studied in 20 mares. Retrospective inspection of plasma progesterone concentrations indicated that a precipitous decrease occurred during Days 15-17 (Day 0 = ovulation) and was defined as the luteolytic period. Mean percentage of CL with color-Doppler signals for blood flow was maximum on Day 10 (77.3%), and Days 10-14 (49.8%) were defined as the preluteolytic period. The cross-sectional area of the CL decreased progressively from Day 4 (9.0 cm2) to Day 19 (1.5 cm2). Progest...
Allen WR.Four separate components combine to produce the progesterone and biologically active 5 alpha-reduced pregnanes needed to maintain pregnancy in the mare. The primary corpus luteum (CL) is prolonged beyond its cyclical lifespan by the down-regulation of endometrial oxytocin receptors to prevent activation of the luteolytic pathway and its waning progesterone production is supplemented from day 40 of gestation by the formation of a series of accessory CL which develop in the maternal ovaries as a result of the gonadotrophic actions of pituitary FSH and the equine chorionic gonadotrophin (eCG). Fr...
Galvão A, Henriques S, Pestka D, Lukasik K, Skarzynski D, Mateus LM, Ferreira-Dias GM.We hypothesized that cytokines influence luteal angiogenesis in mares, while angiogenic factors themselves can also regulate luteal secretory capacity. Therefore, the purpose of this study was to evaluate the role of cytokines--tumor necrosis factor alpha (TNF), interferon gamma (IFNG) and Fas ligand (FASL)--on in vitro modulation of angiogenic activity and mRNA level of vascular endothelial growth factor A (VEGF), its receptor VEGFR2, thrombospondin 1 (TSP1), and its receptor CD36 in equine corpus luteum (CL) throughout the luteal phase. After treatment, VEGF protein expression was determined...
Aurich C, Budik S.Early equine pregnancy shares many features with that of more intensively assessed domestic animals species, but there are also characteristic differences. Some of those are poorly understood. Descent of the equine conceptus into the uterine lumen occurs at day 5 to 6 after ovulation but is only possible when the embryo secretes prostaglandin E2. Although maintenance of equine pregnancy probably involves secretion of a conceptus derived anti-luteolytic factor, this agent has not been identified. Rapid growth, conceptus mobility and presence of an acellular capsule at the time of maternal recog...
de Ruijter-Villani M, van Tol HT, Stout TA.Endometrial oxytocin receptors (OXTR) and prostaglandin-endoperoxide synthase 2 (PTGS2) are central components of the luteolytic pathway in cyclic mares, and their suppression is thought to be critical to luteal maintenance during early pregnancy. We examined the effect of pregnancy on endometrial expression of potential regulators of prostaglandin (PG) F2α secretion in mares. Expression of the nuclear progesterone receptor and oestrogen receptor ERα was high during oestrus, and depressed when progesterone was elevated; the opposite applied to the membrane progesterone receptor. PTGS2 was up...
Alves KA, Alves BG, Gastal GD, de Tarso SG, Gastal MO, Figueiredo JR, Gambarini ML, Gastal EL.Ovarian tissue collected by biopsy procedures allows the performance of many studies with clinical applications in the field of female fertility preservation. The aim of the present study was to investigate the influence of reproductive phase (anestrous vs. diestrous) and ovarian structures (antral follicles and corpus luteum) on the quality, class distribution, number, and density of preantral follicles, and stromal cell density. Ovarian fragments were harvested by biopsy pick-up procedures from mares and submitted to histological analysis. The mean preantral follicle and ovarian stromal cell...
Araujo RR, Ginther OJ.To assess the vascular effects of detomidine and xylazine in pony mares and heifers, respectively, as determined in a major artery and by extent of vascular perfusion of reproductive organs. Methods: 10 pony mares and 10 Holstein heifers. Methods: Pony mares were assigned to receive physiologic saline (0.9% NaCl) solution (n = 5) or detomidine (3.0 mg/mare, IV; 5). Heifers were assigned to receive saline solution (5) or xylazine (14 mg/heifer, IM; 5). Color Doppler ultrasonographic examinations were performed immediately before and 10 minutes after administration of saline solution or sedative...
SHORT RV.A comparison has been made between the steroids present in equine follicular fluid and luteal tissue. Follicular fluid was found to contain progesterone, 17α-hydroxyprogesterone, androstenedione, epitestosterone, 19-norandrostenedione, oestrone, oestradiol-17β and 6α-hydroxyoestradiol-17β, in confirmation of previous studies. On the other hand, luteal tissue contained large amounts of progesterone and 20α-hydroxypregn-4-en-3-one, and a small quantity of 17α-hydroxyprogesterone. No C18 or C19 steroids could be detected.
These findings are therefore interpreted as evidence in favour of ...
Klohonatz KM, Coleman SJ, Islas-Trejo AD, Medrano JF, Hess AM, Kalbfleisch T, Thomas MG, Bouma GJ, Bruemmer JE.Equine maternal recognition of pregnancy (MRP) is a process whose signal remains unknown. During MRP the conceptus and endometrium communicate to attenuate prostaglandin F (PGF) secretion, sparing the corpus luteum and maintaining progesterone production. Recognition of a mobile conceptus by the endometrium is critical by days 14-16 post-ovulation (PO), when endometrium produces PGF, initiating luteolysis. The objective of this study was to evaluate endometrial gene expression changes based upon pregnancy status via RNA sequencing. This experiment utilized a cross-over design with each mare se...
Silva LA, Gastal EL, Beg MA, Ginther OJ.The equine embryonic vesicle is mobile on Days 12-14 (Day 0 = ovulation), when it is approximately 9-15 mm in diameter. Movement from one uterine horn to another occurs, on average, approximately 0.5 times per hour. Mobility ceases (fixation) on Days 15-17. Transrectal color Doppler ultrasonography was used to study the relationship of embryo mobility (experiment 1) and fixation (experiment 2) to endometrial vascular perfusion. In experiment 1, mares were bred and examined daily from Day 1 to Day 16 and were assigned, retrospectively, to a group in which an embryo was detected (pregnant mares;...
Al-zi'abi MO, Watson ED, Fraser HM.Precise pharmacological control of the corpus luteum is important in the manipulation of the oestrous cycle in mares. Angiogenesis plays a key role in the growth and regression of the corpus luteum; therefore, influencing the vasculature of the corpus luteum may offer a novel method for controlling its lifespan. In the present study, changes in angiogenesis and vascular expression of endothelial growth factor (VEGF) were evaluated throughout the luteal phase and after PGF(2alpha)-induced luteolysis. Corpora lutea were collected from mares in the early luteal phase (days 3-4), mid-luteal phase ...
Stout TA, Lamming GE, Allen WR.Recent evidence indicates that, in mares, as in the domestic ruminants, oxytocin and its endometrial receptor play important roles in stimulating the pulsatile releases of prostaglandin F2 alpha from the endometrium that effect luteolysis. In the present experiment, continuous administration of oxytocin by subcutaneous minipump to five mares during days 8-20 after ovulation abolished luteolysis in four of them, while all four of the control mares infused similarly with saline underwent luteolysis at the expected time. When oxytocin administration began on day 10, instead of on day 8, after ovu...
Ginther OJ, Beg MA.The profile of circulating progesterone concentration is more dynamic in cattle than in horses. Greater prominence of progesterone fluctuations in cattle than in horses reflect periodic interplay in cattle between pulses of a luteotropin (luteinizing hormone; LH) and pulses of a luteolysin (prostaglandin F2alpha; PGF2alpha). A dose of PGF2alpha that induces complete regression of a mature corpus luteum with a single treatment in cattle or horses is an overdose. The overdose effects on the progesterone profile in cattle are an immediate nonphysiological increase taking place over about 30 min, ...
Swegen A.Maternal recognition of pregnancy (MRP) is a process by which an early conceptus signals its presence to the maternal system and prevents the lysis of the corpus luteum, thus ensuring a maternal milieu supportive of pregnancy continuation. It is a fundamental aspect of reproductive biology, yet in the horse, the mechanism underlying MRP remains unknown. This review seeks to address some of the controversies surrounding the evidence and theories of MRP in the equine species, such as the idea that the horse does not conform to the MRP paradigm established in other species or that equine MRP invo...
Galvão A, Wolodko K, Rebordão MR, Skarzynski D, Ferreira-Dias G.In the present report we describe the involvement of transforming growth factor B1 (TGF) in functional regression and structural luteolysis in the mare. Firstly, TGF and its receptors activin-like kinase (ALK) 5 and TGF receptor 2 were identified in corpus luteum (CL) steroidogenic, endothelial and fibroblast-like cells. Also, TGF and ALK5 protein expression were shown to be increased in Mid-, and Late-CL (p < 0.05). Subsequently, using an in vitro model with Mid-CL cells, we studied the role of TGF on secretory activity and cell viability. Cell treatment with TGF decreased progesterone...
Köhne M, Kuhl J, Ille N, Erber R, Aurich C.For prevention of early conceptus loss in the horse, treatment with progestins has become common practice. In cattle, treatment with human chorionic gonadotrophin (hCG) during the early postovulatory phase stimulates endogenous progesterone synthesis, which is an important factor for maintenance of early pregnancy via stimulation of endometrial function and conceptus development. In the present study we have therefore investigated the influence of treatment with hCG either for induction of ovulation or during the early luteal phase on plasma progestin concentrations, size of the corpus luteum ...
Galvão A, Tramontano A, Rebordão MR, Amaral A, Bravo PP, Szóstek A, Skarzynski D, Mollo A, Ferreira-Dias G.Metabolic hormones have been associated with reproductive function modulation. Thus, the aim of this study was: (i) to characterize the immunolocalization, mRNA and protein levels of leptin (LEP), Ghrelin (GHR) and respective receptors LEPR and Ghr-R1A, throughout luteal phase; and (ii) to evaluate the role of LEP and GHR on progesterone (P4), prostaglandin (PG) E2 and PGF2α , nitric oxide (nitrite), tumor necrosis factor-α (TNF); macrophage migration inhibitory factor (MIF) secretion, and on angiogenic activity (BAEC proliferation), in equine corpus luteum (CL) from early and mid-luteal sta...
Beyer T, Rink BE, Scarlet D, Walter I, Kunert S, Aurich C.In the horse, it is still unclear if and to what extent low progestin concentration contributes to early conceptus loss. In the present study, we have investigated if reduced or elevated progestin concentration in the early luteal phase influences endometrial function and conceptus development. We hypothesized that reduced progestin concentration via delayed downregulation of endometrial progesterone receptors (PR) influences endometrial function in healthy fertile mares while progestin substitution does not. Genitally healthy estrous mares (n = 8; age 4-14 years) were inseminated and trea...
Townson DH, Pierson RA, Ginther OJ.Plasma progesterone concentrations in mares were determined in two experiments during the time that the luteal glands were detectable by transrectal ultrasonography. In both experiments, corpora lutea were classified into two types of morphologies based on their ultrasonic appearance: centrally nonechogenic luteal glands (fluid-filled) and uniformly echogenic luteal glands (non-fluid-filled). In Experiment 1, daily blood samples were taken from horse mares during August through October and May through July. There were no significant effects of season or luteal morphology on progesterone concen...
Klohonatz KM, Nulton LC, Hess AM, Bouma GJ, Bruemmer JE.Maternal recognition of pregnancy (MRP) in the mare is an unknown process. In a non-pregnant mare on day 14 post-ovulation (PO), prostaglandin F2α (PGF) is secreted by the endometrium causing regression of the corpus luteum. Prior to day 14, MRP must occur in order to attenuate secretion of PGF. The embryo is mobile throughout the uterus due to uterine contractions from day of entry to day 14. It is unknown what signaling is occurring. Literature stated that infusing oil or placing a glass marble into the equine uterus prolongs luteal lifespan and that in non-pregnant mares, serum exosomes co...
Klein C."Maternal recognition of pregnancy" (MRP) is commonly used to describe the ongoing embryo-maternal communication during early pregnancy that culminates in prevention of luteolysis and ensures ongoing progestin support. The conceptus-derived pregnancy recognition signal has not yet been identified in the mare. Although equine conceptuses produce substantial amounts of estrogens, there is a lack of evidence that estrogens are the pregnancy recognition signal in mares. Conceptus mobility is integral to MRP and is driven by conceptus-derived prostaglandin production. Cessation of conceptus mobilit...
Ferreira-Dias G, Bravo PP, Mateus L, Redmer DA, Medeiros JA.Corpus luteum growth and endocrine function are closely dependent on the formation of new capillaries. The objectives of this study were to evaluate (i) tissue growth and microvascular development in the equine cyclic luteal structures; (ii) in vitro angiogenic activity of luteal tissues in response to luteotrophic (LH, PGE(2)) and luteolytic (PGF(2alpha)) hormones and (iii) to relate data to luteal endocrinological function. Our results show that microvascular density was increased in the early and mid luteal phase, followed by a fall in the late luteal phase and a further decrease in the cor...
