The endocrine system in horses comprises a network of glands and hormones that regulate various physiological processes, including metabolism, growth, reproduction, and stress response. Key components of the equine endocrine system include the pituitary gland, thyroid gland, adrenal glands, and pancreas. Hormones such as insulin, cortisol, and thyroid hormones are produced and released into the bloodstream to maintain homeostasis and respond to internal and external stimuli. Dysregulation of the endocrine system can lead to conditions such as Equine Cushing's Disease (Pituitary Pars Intermedia Dysfunction) and Equine Metabolic Syndrome. This page compiles peer-reviewed research studies and scholarly articles that explore the structure, function, and disorders of the endocrine system in horses, providing insights into its impact on equine health and management.
Ginther OJ, Baldrighi JM, Castro T, Wolf CA, Santos VG.In experiment 1, daily blood samples were available from Days 0 to 20 (Day 0 = ovulation) in mares with an interovulatory interval (IOI, n = 5) and in mares that developed idiopathic persistent corpus luteum (PCL, n = 5). The PCL was confirmed by maintenance of progesterone (P4) concentration until end of the experiment (Day 20). Significant interactions of group and day revealed the novel findings that luteinizing hormone (LH) was lower (P < 0.05) in the PCL group than that in the IOI group on Days 0 to 4, and prolactin was lower (P < 0.05) on Days 1, 4, 6, and 7. In experiment 2, treat...
Jellyman JK, Valenzuela OA, Fowden AL.Adrenal glucocorticoids, such as cortisol, are essential for normal fetal development and for maintaining homeostasis in adults. Developmental studies in humans and other animals have shown that exposure to excess glucocorticoids during critical windows of perinatal development can program permanent changes in hypothalamic-pituitary-adrenal (HPA) axis function and metabolic function, with adverse implications for the long-term health of the exposed offspring. The current review compares the programming of postnatal HPA axis function and glucose homeostasis among different species overexposed p...
de Ruijter-Villani M, Stout T.Implantation is a pivotal step in the establishment of mammalian pregnancy. Although implantation strategies vary between species, many aspects of conceptus-maternal signalling necessary to induce uterine receptivity to implantation are conserved. The temporal 'window' for the initiation of implantation is short and precisely controlled by endocrine, paracrine and autocrine factors. An invariable prerequisite for the development of uterine receptivity to implantation is continuous exposure of the endometrium to progesterone which, after a species-specific interval, downregulates progesterone r...
This supplement contains a diverse selection of abstracts addressing clinical research from many disciplines. Topics that are particularly well represented this year include endocrinology, laminitis, critical care and spinal disease. The only consistent feature is the very high standard.
This year, BEVA has devoted an extra two sessions to abstracts, but despite this increased time, the selection process was difficult due to the large number of excellent submissions. Over the last 10 years or so, Clinical Research Abstracts have progressively risen in stature and it is now the go-to place f...
Lotstra RJ, van den Broek J, Power T, Marr CM, Wijnberg ID.Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited. Objective: To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions. Methods: Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket. Methods: Forty-nine horses treate...
Villas-Boas JD, Dias DP, Trigo PI, Almeida NA, de Almeida FQ, de Medeiros MA.Startle is a fast response elicited by sudden acoustic, tactile, or visual stimuli in a variety of animals and in humans. As the magnitude of startle response can be modulated by external and internal variables, it can be a useful tool to study reaction to stress. Our study evaluated whether acupuncture can change cardiac autonomic modulation (heart rate variability); and behavioural (reactivity) and endocrine (cortisol levels) parameters in response to startle. Brazilian Sport horses (n = 6) were subjected to a model of startle in which an umbrella was abruptly opened near the horse. Before s...
Kullmann A, Weber PS, Bishop JB, Roux TM, Norby B, Burns TA, McCutcheon LJ, Belknap JK, Geor RJ.Hyperinsulinaemia is implicated in the pathogenesis of endocrinopathic laminitis. Insulin can bind to different receptors: two insulin receptor isoforms (InsR-A and InsR-B), insulin-like growth factor-1 receptor (IGF-1R) and InsR/IGF-1R hybrid receptor (Hybrid). Currently, mRNA expression of these receptors in equine tissues and the influence of body type and dietary carbohydrate intake on expression of these receptors is not known. Objective: The study objectives were to characterise InsR-A, InsR-B, IGF-1R and Hybrid expression in lamellar tissue (LT) and insulin responsive tissues from horse...
Spelta CW.Equine pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of the hypothalamus, resulting in the loss of dopaminergic inhibition of pars intermedia. An oxidative stress injury of unknown etiology has been suggested to initiate the neurodegeneration. While hypertrichosis (formerly known as hirsutism) is considered pathognomic for advanced disease, the antemortem diagnosis of subclinical and early disease has continued to prove difficult. Numerous tests have been used with varying sensitivities and specificities. The overnight dexamethasone suppression test, originally do...
Morgan R, Keen J, McGowan C.Laminitis is one of the most common and frustrating clinical presentations in equine practice. While the principles of treatment for laminitis have not changed for several decades, there have been some important paradigm shifts in our understanding of laminitis. Most importantly, it is essential to consider laminitis as a clinical sign of disease and not as a disease in its own right. Once this shift in thinking has occurred, it is logical to then question what disease caused the laminitis. More than 90 per cent of horses presented with laminitis as their primary clinical sign will have develo...
Mendoza FJ, Aguilera-Aguilera R, Gonzalez-De Cara CA, Toribio RE, Estepa JC, Perez-Ecija A.Glucose-insulin dynamic challenges such as the intravenous glucose tolerance test (IVGTT) and combined glucose-insulin test (CGIT) have not been described in donkeys. The objectives of this study were (1) to characterize the IVGTT and CGIT in healthy adult donkeys, and (2) to establish normal glucose-insulin proxies. Sixteen donkeys were used and body morphometric variables obtained each. For the IVGTT, glucose (300 mg/kg) was given IV. For the CGIT, glucose (150 mg/kg) followed by recombinant insulin (0.1 IU/kg) were administered IV. Blood samples for glucose and insulin determinations were c...
Lester SJ, Mollat WH, Bryant JE.This article is intended to serve as a reference for clinical pathology in the equine with algorithms and tables provided for anemia diagnosis and leukogram alterations associated with both acute and chronic inflammation. A table of reference is provided for fluid evaluations including joint fluid and effusions into body cavities. Evaluation of newer serum markers, such as cardiac troponin, and a table highlighting test procedures for the evaluation of endocrine disease in the horse are included. A brief overview of quality assurance in the laboratory is provided to stimulate interest in this ...
Mizukami H, Suzuki T, Nambo Y, Ishimaru M, Naito H, Korosue K, Akiyama K, Miyata K, Yamanobe A, Nagaoka K, Watanabe G, Taya K.Development and endocrine changes in Thoroughbreds colts and fillies were compared between those reared at two facilities of the Japan Racing Association, the Hidaka Training and Research Center (Hidaka) and Miyazaki Yearling Training Farm (Miyazaki). Thoroughbred colts and fillies born in Japan between 2003 and 2010 were used. Each colt group and filly group was divided into 2 groups, respectively, and raised in Hidaka or Miyazaki for 7 months from September at 1 year old to April at 2 years old. For the growth parameters, the body weight, height at withers, and girth and cannon circumference...
Kunii H, Nambo Y, Okano A, Matsui A, Ishimaru M, Asai Y, Sato F, Fujii K, Nagaoka K, Watanabe G, Taya K.The effects of an extended photoperiod (EP) in Thoroughbreds colts and fillies from winter at one year old to spring at two years old on the gonadal functions, coat condition, and endocrine changes were investigated. Sixty-two Thoroughbreds (31 colts and 31 fillies) reared in the Hidaka Training and Research Center (Hidaka), Japan Racing Association were used. Thirty of them (15 colts and 15 fillies) were reared under EP conditions from December 20 to April 10, and the remaining 32 horses were reared under natural light alone as a control group. For EP, a 100-watt white bulb was set near the c...
Morgan RA, Keen JA, McGowan CM.Treatment of equine metabolic syndrome (EMS) is essential to improve insulin sensitivity and reduce the risk of laminitis. Calorie restriction and increased exercise are the mainstays of treatment but there is potential for poor owner compliance. Objective: To determine whether significant weight loss accompanied by improvements in measures of insulin sensitivity can be achieved in horses and ponies with EMS managed by their owners in their normal environment under veterinary guidance. Methods: Retrospective clinical case series. Methods: Horses and ponies attending 2 university hospitals for ...
Santos VG, Bettencourt EM, Ginther OJ.Persistent CL (PCL; n = 10) in mares was studied daily from Day 20 (Day 0 = ovulation) to the ending ovulation. In addition, the 10 days before ovulation at the end of a PCL were compared with the end of an interovulatory interval (IOI; n = 28) during the same months. Concentration of P4, cross-sectional area of CL, and percentage of CL with Doppler signals of blood flow during PCLs remained constant from 64 to about 33 days before the end of luteolysis and then decreased linearly. Concentration of LH between Day 20 and beginning of the ovulatory LH surge increased linearly. A dominant follicl...
Nelis H, Vanden Bussche J, Wojciechowicz B, Franczak A, Vanhaecke L, Leemans B, Cornillie P, Peelman L, Van Soom A, Smits K.Steroids play an important role in mammalian reproduction and early pregnancy. Although systemic changes in steroid concentrations have been well documented, it is not clear how these correlate with local steroid concentrations in the genital tract. We hypothesised that, in the horse, the preimplantation embryo may be subjected to high local steroid concentrations for several days. Therefore, we measured progesterone, 17-hydroxyprogesterone, 17?-oestradiol, testosterone and 17?-testosterone concentrations in equine oviductal tissue by ultra-HPLC coupled with tandem mass spectrometry, and proge...
Mendoza FJ, Estepa JC, Gonzalez-De Cara CA, Aguilera-Aguilera R, Toribio RE, Perez-Ecija A.Donkeys are commonly afflicted by endocrine and metabolic disturbances but few studies have investigated endocrine variables involved in energy regulation and their association with morphometric indices, age or gender in this species. Hemostatic and clinical differences have been demonstrated between horses and donkeys, so to consider both species as metabolically and endocrinologically similar could lead to misdiagnosis. In this study, plasma concentrations of glucose, triglycerides and endocrine factors involved in energy homeostasis (insulin, glucagon, leptin, adiponectin, ghrelin and insul...
Deichsel K, Pasing S, Erber R, Ille N, Palme R, Aurich J, Aurich C.The use of breeding stallions for equestrian competitions requires that fertility is not negatively affected by competition or transport to the competition site. In this study, effects of cortisol release induced by road transport (600 km), adrenocorticotropic hormone (ACTH) administration (3 × 0.5 mg synthetic ACTH) and placebo treatment on semen quality and testosterone release were investigated in Shetland stallions (N = 13) using a crossover design. Saliva for cortisol and blood for testosterone analysis were collected for 10 weeks after treatments. Semen was collected daily for 5 days di...
Ing NH, Brinsko SP, Curley KO, Forrest DW, Love CC, Hinrichs K, Vogelsang MM, Varner DD, Welsh TH.Testicular steroidogenesis and spermatogenesis are negatively impacted by stress-related hormones such as glucocorticoids. The effects of two injections of a therapeutic dose of dexamethasone (a synthetic glucocorticoid, 0.1mg/kg; i.v.) given 24h apart to each of three stallions were investigated and compared to three saline-injected control stallions. Dexamethasone decreased circulating concentrations of cortisol by 50% at 24h after the initial injection. Serum testosterone decreased by a maximum of 94% from 4 to 20h after the initial injection of dexamethasone. Semen parameters of the dexame...
Santos VG, Castro T, Bettencourt EM, Ginther OJ.A procedure for oxytocin (OT) administration on Day 13 postovulation was developed in mares for stimulation of a pulse of PGFM (a PGF2α metabolite) that mimics a natural PGFM pulse during luteolysis. Bolus treatment with each of five OT doses (1-10 IU/mare, n = 3) stimulated a burst of PGFM that was maximum in 4 minutes and was unlike a natural pulse. A 2-hour OT infusion of 1.25, 2.5, or 5 IU/100 kg (n = 4) induced a PGFM pulse similar to reported pulses; lower doses did not. The peak of an induced pulse (approximately 260-380 pg/mL) seemed similar to reported natural peaks (approxima...
Santos VG, Bettencourt EM, Ginther OJ.Mares with persistent CL (PCL) with no known etiology (idiopathic) were matched with mares with an interovulatory interval (IOI) of apparent physiological length, so that ovulation at the beginning of each PCL and IOI occurred during the same month (n = 6/group). Blood samples were collected daily from Days 12 to 22 (Day 0 = ovulation). Mean progesterone (P4) decreased in both groups on Days 14 and 15 and then diverged with a continued decrease in the IOI group and the beginning of constant and greater (P < 0.05) P4 concentration on each day in the PCL group. Before P4 divergence betw...
Beltman ME, Walsh SW, Canty MJ, Duffy P, Crowe MA.The objective was to characterise the hormonal composition of follicular fluid from mares with distinct anovulatory-cystic follicles. Follicular fluid was aspirated from six mares that presented with cystic follicles and from pre-ovulatory follicles of five normal mares (controls). Differences in progesterone, oestradiol, testosterone, IGF-I and IGF binding were analysed using Fisher's exact test. There were greater (P < 0.03) follicular fluid oestradiol concentrations in normal follicles and the testosterone concentration of the cystic fluid was greater (P < 0.05) than that of t...
Karikoski NP, McGowan CM, Singer ER, Asplin KE, Tulamo RM, Patterson-Kane JC.Laminitis in equids is a clinical syndrome usually associated with systemic disease. Endocrinopathies recently have been recognized as the most common cause of laminitis, with hyperinsulinemia playing a key role. Descriptions of laminitis-associated lesions have been confusing due to the wide range of experimental models used, failure of adequate clinical documentation for naturally occurring cases, lack of separate analysis of inflammatory and endocrinopathic laminitis, and uncertainty regarding normal morphological variation of lamellae. In this study, lamellar morphology and pathology were ...
Saengtienchai A, Ikenaka Y, Nakayama SM, Mizukawa H, Kakehi M, Bortey-Sam N, Darwish WS, Tsubota T, Terasaki M, Poapolathep A, Ishizuka M.Interspecific differences in xenobiotic metabolism are a key to determining relative sensitivities of animals to xenobiotics. However, information on domesticated livestock, companion animals, and captive and free-ranging wildlife is incomplete. The present study evaluated interspecific differences in phase II conjugation using pyrene as a nondestructive biomarker of polycyclic aromatic hydrocarbon (PAH) exposure. Polycyclic aromatic hydrocarbons and their metabolites have carcinogenic and endocrine-disrupting effects in humans and wildlife and can have serious consequences. The authors collec...
Jellyman JK, Valenzuela OA, Allen VL, Forhead AJ, Holdstock NB, Fowden AL.The present study tested the hypothesis that overexposure to endogenous glucocorticoids in neonatal life alters the reactivity of the hypothalamic-pituitary-adrenal (HPA) axis in ponies at 1 and 2 yr of age. Newborn foals received saline (0.9% NaCl, n = 8, control) or long-acting adrenocorticotropic hormone (ACTH1-24) (Depot Synacthen 0.125 mg intramuscularly twice daily, n = 9) for 5 d after birth to raise cortisol concentrations 5- to 6-fold. At 1 and 2 yr of age, HPA axis function was assessed by bolus administration of short-acting ACTH1-24 (1 μg/kg intravenous) and insulin (0.5 U/kg...
Banse HE, McCann J, Yang F, Wagg C, McFarlane D.Diagnosis of equine hyperinsulinemia requires an accurate method for quantification of equine insulin concentrations. The objectives of the current study were to compare 2 commercially available techniques for measurement of equine insulin, the radioimmunoassay (RIA) and chemiluminescent immunoassay (CIA). Recovery was poor for both assays, but worse for the CIA. Serial dilution of a high endogenous insulin sample yielded better linearity for the RIA ( r = 0.99, P < 0.001) than the CIA ( r = 0.92, P = 0.009). Bland-Altman analysis indicated that the CIA was, on average, 91 pmol/l higher tha...
Iacono E, Merlo B, Rizzato G, Mislei B, Govoni N, Tamanini C, Mari G.The aim of the present study was to verify how repeated ovum pick-up (OPU), performed in anestrous and cyclic mares, affect ovarian activity, measured by progesterone (P4) and 17ß-estradiol (E2) plasma levels. Ovum pick-up of all visible follicles was performed every 9 to 12 days, and four sessions were carried out during anestrous (A) and breeding season (BS). The number of aspirated follicles per mare at each session was not significantly different between the two periods (BS: 6.1 ± 2.4; A: 7.5 ± 4.4; P > 0.05), but the mean follicular diameter was significantly higher during BS (16.0 ...
Nagel C, Erber R, Ille N, von Lewinski M, Aurich J, Möstl E, Aurich C.External and internal stressors prolong parturition in different species. At parturition, sympathoadrenal activation should be avoided because an increased sympathetic tone may cause uterine atonia via β2-receptors. We hypothesized that at physiological parturition, horses are under parasympathetic dominance, and stress-response mechanisms are not activated during delivery of the foal. To evaluate stress responses, heart rate, heart rate variability, catecholamines, and cortisol were analyzed in mares (n = 17) throughout foaling. Heart rate decreased from 2 hours before (51 ± 1 beats/minute)...
Mejia-Pereira S, Perez-Ecija A, Buchanan BR, Toribio RE, Mendoza FJ.Endocrine disorders are common in donkeys. Pituitary pars intermedia dysfunction (PPID) is thought to be a frequent disturbance in donkeys due to their longevity. However, information on PPID dynamic testing in donkeys is lacking. Objective: The objective of this study was to evaluate the previously described guidelines for PPID diagnosis in horses in donkeys with suspicion of PPID. Methods: Prospective experimental study. Methods: Eighty donkeys were evaluated for PPID suspicion based on clinical signs and baseline adrenocorticotropic hormone (ACTH) concentrations. Six mix-breed donkeys (one ...
Forhead AJ, Broughton Pipkin F, Taylor PM, Baker K, Balouzet V, Giussani DA, Fowden AL.Blood pressure, heart rate and the plasma concentrations of cortisol and components of the renin-angiotensin system were measured in chronically catheterized Pony mares (n=15) and their fetuses during the second half of gestation (day 153-336 of gestation; term is normally between day 320 and day 340 of gestation). Fetal blood pressure increased towards term with the prepartum surge in plasma cortisol concentration, and there was a correlation between fetal blood pressure and both gestational age (r = 0.88, P < 0.0005) and plasma cortisol concentration (r = 0.88, P < 0.0005). Plasma concentrat...
Delank K, Reese S, Erhard M, Wöhr AC.This study had the aim to demonstrate the midterm effects (three weeks) of weaning on foals' welfare. For this purpose, foals' behavioral changes and fecal levels metabolites of cortisol were evaluated. The observations took place at the state stud farm of Baden-Wuerttemberg in Germany. Ten foals (six colts and four fillies) were observed from one day before weaning up until three weeks after weaning. Weaning was divided into three blocks, the first in September, the second in October, and the last in November. The behavioral observation was done during an eight-hour period between 7:00 a.m. a...
Golland LC, Evans DL, Stone GM, Tyler-McGowan CM, Hodgson DR, Rose RJ.The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body...
Conley AJ, Ball BA.Historically, studies on the endocrinology of pregnancy and parturition in horses have made major contributions of relevance to mammals in general. Recent use of liquid chromatography mass spectrometry, measuring multiple steroid hormones simultaneously in blood, foetal and placental tissues throughout normal gestation, and in mares with experimentally induced placentitis, has advanced our current understanding of many of the unusual strategies seen during gestation and at foaling. This includes the stimulation of luteal steroidogeneisis by equine chorionic gonadotropin (eCG) from the endometr...
McGowan CM, Neiger R.Trilostane, a competitive 3-beta hydroxysteroid dehydrogenase inhibitor, has been used successfully to control clinical signs and cortisol excess in canine pituitary dependent hyperadrenocorticism. Objective: Trilostane was evaluated for its efficacy in resolving clinical and clinicopathological abnormalities of equine Cushing's syndrome (ECS) and to assess its safety. Methods: Twenty horses (mean age 21 years) diagnosed with ECS were followed for 1 or 2 years. Affected horses received 0.4-1 mg/kg (mean 0.5 mg/kg) trilostane once daily. Results: Clinical signs assessed over 1 or 2 years, showe...
Holdstock NB, Allen VL, Bloomfield MR, Hales CN, Fowden AL.At birth, the endocrine pancreas must assume a glucoregulatory role if the neonate is to survive the transition from parenteral to enteral nutrition. In species like the horse, neonatal hypoglycaemia is common, which suggests that the glucoregulatory mechanisms are not always fully competent at birth. Hence, this study examined pancreatic beta cell function in newborn foals during nutritional adaptation over the first 10 days post partum. Over a 48 h period at three time intervals after birth (days 1-2, 5-6 and 9-10 post partum), the beta cell responses to suckling and to intravenous administr...
Donadeu FX, Watson ED.The annual reproductive cycle in the horse involves a reduction in ovarian activity during short days. The absence of ovulatory activity during winter has important consequences for an equine industry eager to breed mares early during the year. The anovulatory season results from a reduction in the secretion of pituitary gonadotropin that is in turn triggered by the inhibitory effects of short photoperiod on the hypothalamus-pituitary axis. Recent studies have provided evidence that the response of the ovaries to endocrine stimuli during the anovulatory season is affected not only by circulati...
Scholtz EL, Krishnan S, Ball BA, Corbin CJ, Moeller BC, Stanley SD, McDowell KJ, Hughes AL, McDonnell DP, Conley AJ.One of the most widely accepted axioms of mammalian reproductive biology is that pregnancy requires the (sole) support of progesterone, acting in large measure through nuclear progesterone receptors (PRs) in uterine and cervical tissues, without which pregnancy cannot be established or maintained. However, mares lack detectable progesterone in the latter half of pregnancy. Instead of progesterone, several (mainly 5α-reduced) pregnanes are elevated and have long been speculated to provide progestational support in lieu of progesterone itself. To the authors' knowledge, evidence for the bioacti...
Cudd TA, LeBlanc M, Silver M, Norman W, Madison J, Keller-Wood M, Wood CE.Fetal maturation and the timing of parturition in both sheep and primates are thought to be controlled by the hypothalamic-pituitary-adrenal axis but little is known about the endocrinology of the equine fetus. We investigated the ontogeny of plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol and corticosteroid binding capacity in the late-gestation fetal horse. We also wished to determine whether there is ultradian rhythmic release of ACTH and cortisol in fetal horses and we compared fetuses to maternal and non-pregnant adult horses. Six fetuses, 278-304 days gestation (ter...
Fitzgerald BP, Davison LA, McManus CJ.In seasonally breeding species photoperiodic information is thought to be conveyed to the reproductive and prolactin axis via changes in circulating concentrations of melatonin. For some species, a constant melatonin stimulus is perceived as a short day, whereas in others no photoperiodic information is provided. In the mare, a preliminary study demonstrated that constant administration of melatonin did not modify prolactin secretion, suggesting that this treatment regimen failed to provide photoperiodic information. To further investigate this proposal and to investigate an alternative explan...
De Cock HE, MacLachlan NJ.Neoplastic and hyperplastic disorders that affect multiple endocrine tissues in a single individual are well described in humans but less so in domestic animals. Multiple endocrine neoplasia (MEN) in humans is a genetically determined syndrome characterized by the appearance of benign or malignant proliferations within two or more endocrine glands. The primary endocrine tumors that are characteristic of MEN arise from cells that share the capacity for amine precursor uptake and decarboxylation. Here we describe the case of a 22-year-old Thoroughbred mare that died during an unattended parturit...
Song Y, Massart C, Chico-Galdo V, Jin L, De Maertelaer V, Decoster C, Dumont JE, Van Sande J.In the literature, data obtained in signal transduction from various species thyroids and cells lines are often integrated in a common model. We investigate qualitatively and systematically, using the same protocol, the control by TSH of the two main functions of the thyrocytes, the synthesis and the secretion of thyroid hormones. In all species investigated, the TSH receptor activates both. In some species, including humans, rats and mice, the TSH receptor activates both the cAMP and phospholipase C-PIP2 cascades, in others (e.g. dog) it only stimulates the first. The cAMP pathway activates t...
Ferreira-Dias G, Botelho M, Zagrajczuk A, Rebordão MR, Galvão AM, Bravo PP, Piotrowska-Tomala K, Szóstek AZ, Wiczkowski W, Piskula M, Fradinho MJ....Phytoestrogens exist in plants that are present in forages fed to horses. They may compete with 17-β estradiol and influence the estrous cycle. Therefore, the objective was to determine whether coumestrol from clover-mixed pastures is present in mare's plasma after their ingestion (experiment I), and when this phytoestrogen was present in mare's plasma after ingestion (experiment II). The effect of a long-term ingestion of phytoestrogens on estrous cycle disruption was assessed (experiment III; clinical case). Experiment I was carried out in nonpregnant anestrous and cyclic Lusitano mares (n ...
Pashen RL, Allen WR.The effects of fetal gonadectomy on steroid production and the maintenance of pregnancy in the mare were studied. Removal of the fetal gonads resulted in an immediate fall in maternal plasma concentrations of conjugated and unconjugated oestrogens whereas progestagen levels remained unchanged. Hormone profiles in mares carrying sham-operated fetuses remained similar to those in unoperated control mares. Plasma levels of 13,14-dihydro-15-oxo-PGF-2 alpha (PGFM) were much lower, and uterine contractions weaker, during labour in mares carrying gonadectomized foals than in control mares. Pregnancy ...
Vandeplassche GM, Wesson JA, Ginther OJ.Sexual behavior, follicular development and ovulation, and concentrations of circulating gonadotropins during the estrous cycle were studied during the summer in 7 jennies. Mean behavioral estrous length was 6.4 +/- 0.6 days (mean +/- SEM, n=19; 5.6 +/- 0.5 days preovulatory and 0.8 +/- 0.2 days post-ovulatory). Mean diestrous length was 19.3 +/- 0.6 days (n=14). Females in estrus typically showed posturing, mouth clapping, clitoral winking, urinating and tail raising. Mouth clapping began approximately one day sooner and lasted approximately one day longer than winking and tail raising, so th...
Petrucci L, Maranesi M, Verini Supplizi A, Dall'Aglio C, Mandara MT, Quassinti L, Bramucci M, Miano A, Gobbetti A, Catone G, Boiti C, Zerani M.The objectives of this study were to evaluate in horse testes the expression of kisspeptin (KiSS) and GnRH1 neuropeptides and their cognate receptors, KiSS1R and GnRH1R, as well as their action on testosterone, GnRH1, prostaglandin F2α (PGF2α), and PGE2 synthesis and cyclooxygenase 1 (COX1) and COX2 activity by Leydig cells in vitro. Testes were obtained from 9 sexually mature horses by surgical castration. Immunohistochemistry, evidenced the presence of KiSS, KiSS1R, GnRH, and GnRH1R in Leydig cells, whereas germinal and Sertoli cells were positive only for GnRH1. Transcripts for both neur...
Ginther OJ, Gastal EL, Gastal MO, Beg MA.The functional and temporal relationships between circulating gonadotropins and ovarian hormones in mares during Days 7-27 (ovulation = Day 0) was studied using control, follicle ablation, and ovariectomy groups (n = 6 mares/group). In the follicle-ablation group, all follicles > or = 6 mm were ablated on Day 7, and every 2 days thereafter, newly emerging follicles were also ablated. Estradiol concentrations decreased (P < 0.01) similarly in the controls and the follicle-ablation group between Days 7 and 11 and by Day 15 began to increase in the controls and continued to decrease in the ...
Caraty A, Decourt C, Briant C, Beltramo M.Kisspeptins (Kp) are a family of neuropeptides produced mainly by two hypothalamic neuronal cell populations. They have recently emerged as a major regulator of the gonadotropin axis and their action is located upstream of the gonadotropin-releasing hormone (GnRH) cell population. In less than 10 yr a growing body of literature has demonstrated the involvement of these peptides in most, if not all, aspects of reproductive axis maturation and function. In contrast to these abundant basic research studies, few experiments have evaluated the potential application of Kp as tools to manipulate repr...
Thatcher WW, Bazer FW, Sharp DC, Roberts RM.Processes associated with "Maternal Recognition of Pregnancy" are reviewed extensively from the ovine, bovine, porcine and equine species. Comparisons among these species indicate that CL maintenance is achieved primarily by a predominant antiluteolytic-anti PGF effect, and there is strong evidence for antiluteolytic-luteoprotective and luteotropic controls that complement this basic system. The nature of the chemical signals (steroids, prostaglandins and proteins) to regulate these processes among the species are described. Common to all of the species reviewed is a change in vascular dynamic...
Rota A, Sgorbini M, Panzani D, Bonelli F, Baragli P, Ille N, Gatta D, Sighieri C, Casini L, Maggiorelli MM, Aurich C, Camillo F.Reproductive management of male donkeys employed for artificial breeding has been poorly studied. The aim of this study was to evaluate the effect of housing system, with the animals grouped together in a paddock or kept in individual boxes, on sexual behaviour, cortisol and testosterone concentration and seminal characteristics of adult male donkeys. The study included four Amiata donkey jacks (stallions) from which ejaculates, saliva and blood were collected during two distinct 3 weeks periods, one in the group and one in the box housing system. Time needed for semen collection was shorter ...
Alexander SL, Irvine CH, Donald RA.Since 1985, we have applied our nonsurgical technique for collecting pituitary venous (PitVen) blood from ambulatory horses to investigate the regulation of adrenocorticotropic hormone (ACTH) secretion. This method offers particular advantages for studying the hypothalamo-pituitary-adrenal axis since its benign nature enables hypothalamic and pituitary interactions to be monitored without disturbing the animal, and the horse's large blood volume allows 3- to 4-ml samples to be collected as frequently as every 20s for prolonged periods so that the secretion patterns of ACTH and its secretagogue...
Tamanini C, Giordano N, Chiesa F, Seren E.Plasma cortisol variations have been determined by radioimmunoassay in 5 stallions during mating and in 2 teasers during oestrous female exposure. In all the animals, cortisol plasma levels consistently increase (71.1 ng/ml vs 44.0 and 63.0 ng/ml vs 35.1, in the stallions and in the teasers, respectively) 7-30 min after female exposure; 120 min after exposure, cortisol concentrations are again low.
Lemazurier E, Moslemi S, Sourdaine P, Desjardins I, Plainfosse B, Seralini GE.The steroid content of semen from a total of 11 mature fertile stallions was studied during two breeding seasons and one winter. The levels of free and conjugated substrates (testosterone and androstenedione), and products (estradiol and estrone), of aromatase were measured by radioimmunoassay with a validated method. The results were seasonally and monthly highly variable with characteristic peaks. The concentrations of free and conjugated estrogens were always higher in the gel-free ejaculate than in the gel except in one subfertile stallion used as comparison. Furthermore, the steroid produ...
Satué K, Marcilla M, Medica P, Ferlazzo A, Fazio E.Androgens modulate maternal ovarian activity, embryo implantation and correct placental development. The objective of this study was to establish reference values for testosterone (T), androstenedione (A4) and dehydroepiandrosterone (DHEA) concentrations in pregnant mares. A total of 30 healthy Spanish Purebred mares with an age range of 9.33 ± 3.31 years, were studied during the 11 months of gestation. T, A4 and DHEA concentrations were determined using EIA validated specifically for equines. T increased in the 2nd and 3rd month (P < 0.05), showing a plateau between the 4th and 6th m...
Cravana C, Medica P, Prestopino M, Fazio E, Ferlazzo A.Limited knowledge exists about the differentiated effects of competitive and noncompetitive showjumping on thyroid function and relationships with hypothalamic-hypophysis-corticoadrenal hormones. Objective: To obtain preliminary data about differentiated effects of competitive and noncompetitive showjumping on total and free iodothyronines, β-endorphin, ACTH and cortisol of horses. Methods: Five trained healthy jumper horses were studied during competitive and noncompetitive showjumping, performed in the same circuit design over 10 fences of 1.10 m. Hormone levels before, 5 and 30 min post ex...
Durward-Akhurst SA, Schultz NE, Norton EM, Rendahl AK, Besselink H, Behnisch PA, Brouwer A, Geor RJ, Mickelson JR, McCue ME.Equine Metabolic Syndrome (EMS) is characterized by abnormalities in insulin regulation, increased adiposity and laminitis, and has several similarities to human metabolic syndrome. A large amount of environmental variability in the EMS phenotype is not explained by commonly measured factors (diet, exercise, and season), suggesting that other environmental factors play a role in EMS development. Endocrine disrupting chemicals (EDCs) are associated with metabolic syndrome and other endocrine abnormalities in humans. This led us to hypothesize that EDCs are detectable in horse plasma and play a ...
