Steroid hormones in horses are biologically active compounds that are synthesized from cholesterol and play a significant role in various physiological processes. These hormones include glucocorticoids, mineralocorticoids, and sex steroids such as estrogens, androgens, and progestogens. They are involved in regulating metabolism, immune function, electrolyte balance, and reproductive functions. The levels of steroid hormones can be influenced by factors such as age, sex, stress, and disease states. Understanding their regulatory mechanisms and effects is essential for managing equine health and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the synthesis, regulation, and physiological roles of steroid hormones in horses.
Donadeu FX, Ginther OJ.The temporal relationships in the changes in concentrations of follicular fluid factors during follicle selection were characterized in mares. All follicles > or =5 mm were ablated 10 days after ovulation, followed by follicular fluid collection from the three largest follicles (F1, F2, and F3) when F1 of the new wave reached a diameter of 8.0-11.9, 12.0-15.9, 16.0-19.9, 20.0-23.9, 24.0-27.9, or 28.0-31.9 mm (n = 4-8 mares/range). Diameter deviation between F1 and F2 began during the 20.0- to 23.9-mm range, as indicated by a greater difference in diameter between the two follicles at the 24...
Palme R, Entenfellner U, Hoi H, Möstl E.Non-invasive pregnancy diagnosis in mares by measuring faecal oestrogens has been performed over years with great accuracy. However, results have indicated breed-related differences in the amount of excreted steroids during late pregnancy. Therefore faecal samples were collected during the last 4 months of pregnancy of Thoroughbred (n = 10), New Forest pony (n = 9), Shetland pony (n = 10) and Iceland pony mares (n = 11). Concentrations of oestrogens, 20alpha-hydroxy- and 20-oxopregnanes were measured using enzyme immunoassays. Breed differences concerning both levels (though significant only i...
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...
Bridges TS, Davidson TR, Chamberlain CS, Geisert RD, Spicer LJ.The objective of the present study was to evaluate changes in equine follicular fluid insulin-like growth factor binding protein (IGFBP) proteolytic activity as well as steroid, IGF, and IGFBP concentrations during follicular development in the mare. Mares (n = 14) were classified as either in the follicular phase (n = 8) or luteal phase (n = 6). Follicles (n = 92) were categorized as small (6 to 15 mm; n = 54), medium (16 to 25 mm; n = 23), or large (> 25 mm; n = 15), and follicular fluid was collected. Estradiol and androstenedione levels in follicular fluid were greater (P < 0.05), an...
Dehennin L, Bonnaire Y, Plou P.Dehydroepiandrosterone (DHEA) and androstenedione are weak androgens, which need conversion to more potent testosterone in order to enhance anabolic action. Consequences of oral dosing at 1 mg/kg on the urinary and plasma androgen profile of mare and gelding have been evaluated with an analytical method involving conjugate fractionation and selective hydrolysis, group separation, and quantitation by gas chromatography-mass spectrometry with selected ion monitoring of trimethylsilyl ethers. Peak levels of testosterone total conjugates in urine (range 300-6000 microg/L) were attained a few hours...
Lee ST, Stegelmeier BL, Gardner DR, Vogel KP.Switchgrass (Panicum virgatum L.) has been reported to be hepatotoxic, causing photosensitization in lambs and horses. In this study we show the presence of steroidal saponins in two samples of switchgrass that has been implicated in the poisonings of sheep and horses. After hydrolysis of the saponins, diosgenin was determined to be the major sapogenin in both switchgrass samples. We also confirmed the presence of diosgenin in kleingrass after hydrolysis of saponins extracted from it.
Baltsen M, Bøgh IB, Byskov AG.Meiosis activating sterols (MAS) are pre-cholesterol sterols that can be isolated from follicular fluid (FF-MAS) or testes (T-MAS). Meiosis activating sterols trigger the resumption of meiosis in cultured meiotically competent oocytes. In the present work MAS, cholesterol and progesterone were assayed by HPLC in follicular fluids collected from pony mares at fixed days after the last ovulation. Follicles were divided into two groups according to whether they were aspirated before or after Day 17 after the last ovulation. The latter group was further divided according to whether the follicle di...
Lemazurier E, Sourdaine P, Nativelle C, Plainfossé B, Séralini G.Adult stallion secretes very high estrogen levels in its testicular vein and semen, and the responsible enzyme cytochrome P450 aromatase (P450 arom) is known to be present mainly in Leydig cells. We studied in further details the distribution of equine aromatase in various adult tissues including the brain (hypothalamic area), liver, kidney, small intestine, muscle, bulbourethral gland and testes. The aromatase mRNA was essentially detected by RT-PCR in testis (169+/-14 amol of aromatase mRNA per microg of total RNA) and was barely detectable in brain, or below 0.1 amol/microg RNA in other tis...
Sharp DC, Wolfe MW, Cleaver BD, Nilson J.The process of sexual recrudescence in the springtime in mares is characterized by renewal of follicular growth and acquisition of steroidogenic competence. Concomitant with renewal of follicular steroidogenesis is re-establishment of LH biosynthesis and secretion. Research results from our laboratory indicate that increased estradiol and LH secretion occur in close temporal association before the first ovulation of the year. Therefore, the hypothesis tested in this experiment was that estrogen administration to ovariectomized pony mares during the equivalent time of early vernal transition wo...
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 ...
Albrecht BA, MacLeod JN, Daels PF.In the pregnant mare, luteal estrogen production increases at the onset of equine chorionic gonadotropin (eCG) secretion by endometrial cups. In previous studies, we have demonstrated that eCG stimulates luteal androgen and estrogen production in pregnant mares. To further elucidate the regulation of steroidogenesis within the equine corpus luteum (CL) of pregnancy, we examined the expression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/17,20 lyase (P450(17alpha)) and cytochrome P450 aromatase (P450(arom)) in luteal tissue samples collected during dies...
Boerboom D, Pilon N, Behdjani R, Silversides DW, Sirois J.Steroidogenic factor-1 (SF-1, NR5A1a) is a member of the NR5A nuclear receptor subfamily and has been implicated as a key transcriptional regulator of all ovarian steroidogenic genes in vitro. To establish links between the expression of SF-1 and that of the steroidogenic genes in vivo, the objectives of this study were to clone equine SF-1 and examine the regulation of its messenger RNA (mRNA) in follicular cells during human CG (hCG)-induced ovulation. The equine SF-1 primary transcript was cloned by a combination of RT-PCR techniques. Results showed that the transcript was composed of a 5'-...
Marshall DE, Mortishire-Smith RJ, Houghton E, Gower DB.Oestradiene-3,17-diol and oestratriene-3,17-diol (or the diol of Heard's ketone (3-hydroxy-5(10),6,8-oestratriene-17-one) have been extracted on a large scale from pooled urines and allantoic fluid obtained from pregnant mares. Initial purification was achieved using column chromatography, and further purification by high performance liquid chromatography or silver nitrate (argentation) thin layer chromatography. The steroids were characterised using gas chromatography-mass spectrometry. Positions of the double bonds in ring B of oestradienediol were deduced on the basis of results of ultravio...
Watson ED, Thomson SR, Howie AF.A steroidogenic acute regulatory (StAR) protein has been identified in several species as a probable important rate-limiting step in steroidogenesis. This protein is believed to be responsible for transporting cholesterol from the outer to the inner mitochondrial membrane. It is known that equine chorionic gonadotrophin (eCG) stimulates steroidogenesis in the corpora lutea of early pregnant mares and that eCG also upregulates StAR mRNA in bovine ovaries. In the present study, ovarian tissue from cyclic and early pregnant mares was immunostained to detect the distribution of the StAR protein. W...
Aupperle H, Ozgen SSchoon HA, Schoon D, Hoppen HO, Sieme H, Tannapfel A.The aims of this study were to investigate the steroid hormone receptor expression and the proliferation intensity during the equine endometrial cycle by immunohistological methods, established for routine examination of formalin-fixed, paraplast-embedded specimens. Endometrial biopsy specimens were obtained during one cycle from 7 mares. In comparison with the blood steroid hormone levels the quantity and distribution of oestrogen (ER) and progesterone receptors (PR) and the proliferation marker Ki-67 antigen expression were investigated. Rising 17beta-oestradiol concentrations in preoestrus ...
Belin F, Goudet G, Duchamp G, Gérard N.The objective of the present study was to determine the changes in follicular fluid steroid concentrations and in granulosa cell steroidogenic enzyme expression during the follicular phase, in relation to follicular size and physiological status in the mare. Follicular fluid and follicular cells were recovered by ultrasound-guided follicular punctures either around the time of emergence of the dominant follicle, at the end of the dominant follicle growth, or at the preovulatory stage, after injection of gonadotropin to induce ovulation. Cellular relative amounts of steroidogenic acute regulato...
McDowell KJ, Adams MH, Adam CY, Simpson KS.Two experiments were performed to determine changes in the abundance of oestrogen and progesterone receptor (ER alpha and PR) mRNAs in equine endometrium during the oestrous cycle and early pregnancy, and under the influence of exogenous steroids. In Expt 1, endometrial biopsies were obtained from non-mated mares during oestrus and at days 5, 10 and 15 after ovulation, and from pregnant mares at days 10, 15 and 20 after ovulation. There were overall effects of day on the abundance of ER alpha (P = 0.0001) and PR (P = 0.0014) mRNAs. The amount of ER alpha mRNA decreased at day 10 of pregnancy, ...
Möstl E, Messmann S, Bagu E, Robia C, Palme R.After 14C-labelled cortisol infusion in ponies and pigs, faecal samples were collected. Extraction of 0.5 g faeces with 5 ml 80-90% methanol yielded the highest radioactivity in the supernatant. Most of the metabolites were ether soluble. After high performance liquid chromatography (HPLC), the presence of immunoreactive metabolites was demonstrated by measuring each HPLC fraction using enzyme immunoassays for cortisol, corticosterone and 11-oxoaetiocholanolone. Only the assay for 11-oxoaetiocholanolone revealed peaks with co-eluting radioactivity. For biological validation of the test system,...
Tanaka Y, Nagamine N, Nambo Y, Nagata S, Nagaoka K, Tsunoda N, Taniyama H, Yoshihara T, Oikawa M, Watanabe G, Taya K.In mares, circulating immunoreactive inhibin concentrations increase during the follicular phase and decrease at the start of the LH surge. Thereafter, sharp increases in circulating immunoreactive inhibin concentrations, the 'ovulatory increase', are observed during ovulation. In the present study, the cellular sources and molecular form of ovarian inhibin were investigated to determine the mechanism responsible for this unique ovulatory increase. Three sizes of ovarian follicles (small, 30 mm in diameter) were selected. Inhibin alpha-subunit was localized by immunohistochemistry to the gran...
Roser JF, Tarleton M, Belanger JM.Recent studies in our laboratory investigating plasma gonadotrophin concentrations before and after castration indicate that the hypothalamic-pituitary axis is not the original site of dysfunction in stallions with idiopathic infertility. In the present study, fertile, subfertile and infertile stallions were subjected to replacement therapy with oestradiol and testosterone 1 year after castration to investigate hypothalamic-pituitary axis function further. Fertile (n=5), subfertile (n=3) and infertile (n=2) castrated stallions of Light horse breeds, aged 11-23 years, were given either oestradi...
Albrecht BA, MacLeod JN, Daels PF.At the onset of equine chorionic gonadotrophin (eCG) secretion, eCG stimulates luteal androgen and oestrogen production. Although eCG concentrations increase exponentially from day 37 to day 60 of gestation and eCG is detectable in maternal serum until about day 120-150 of gestation, luteal androgen and oestrogen production peaks between 5 and 10 days after initial exposure to eCG and then decreases gradually. It is not clear how eCG regulates luteal androgen and oestrogen production. In the present study, the steady-state mRNA expression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cyto...
Taya K, Nagata S, Tsunoda N, Nagamine N, Tanaka Y, Nagaoka K, Taniyama H, Nambo Y, Watanabe G.In this study, clear seasonal changes in the circulating concentrations of immunoreactive inhibin were observed in stallions throughout the year. The highest plasma concentrations of immunoreactive inhibin were observed during the breeding season and the lowest concentrations were observed during the nonbreeding season. There was positive correlation between the circulating concentrations of immunoreactive inhibin, steroid hormones and gonadotrophins. Inhibin alpha subunit positive staining was observed in Sertoli cells and more clearly in Leydig cells. Both cell types also stained positively ...
Gerstenberg C, Allen WR.Branched tubular endometrial glands are key features of the uterine lining in mares. The epithelium in the neck regions of the glands is similar to that lining the lumen of the uterus, whereas the epithelium in the deeper, coiled portions of the glands secretes protein rich histotrophe or 'uterine milk' during dioestrus and pregnancy. The present study was performed to characterize endometrial histology in perinatal and peripubertal fillies and to investigate the influences of specific steroid treatments on endometrial gland development in the prepubertal period. Uteri obtained from equine fet...
Behrendt-Adam CY, Adams MH, Simpson KS, McDowell KJ.In this study, the roles of oestrogen and progesterone in the regulation of oxytocin gene expression in equine endometrium were examined. Anoestrous mares (n=19) were assigned randomly to one of the following treatment groups: control (vehicle control for 1 day; n=3); progesterone (250 mg progesterone per day for 6 days; n=4); oestradiol (5 mg beta-oestradiol 17-valerate per day for 6 days; n=4); oestradiol plus short duration progesterone (5 mg beta-oestradiol 17-valerate per day for 6 days followed by 250 mg progesterone per day for 6 days; n=4); and oestradiol plus long duration progesteron...
Chavatte-Palmer P, Duchamp G, Palmer E, Ousey JC, Rossdale PD, Lombès M.Progesterone, oestrogen and glucocorticoid receptor concentrations in the uterus and mammary glands of pregnant mares during mid- to late gestation (from day 150 of gestation to term) were measured by binding assays to investigate the hormonal mechanisms involved in pregnancy maintenance and lactation. Uterine progesterone receptor concentrations did not increase significantly with increasing gestational age (from 67.8 +/- 13.7 to 126.1 +/- 48.7fmol mg(-1) protein), whereas oestrogen receptor concentrations were significantly higher in pregnant mares (271.7 +/- 28.9 fmol mg(-1) protein) than i...
Hoffmann B, Landeck A.To gain further information on gonadal function of the stallion, concentrations of testicular steroids in blood plasma (bpl) and seminal plasma (spl) and their distribution in the ejaculate were determined. Blood and semen samples from a total of 11 stallions were collected from November to July. Estrone (E1), estrone sulfate (E1S), estradiol-17beta (E2beta) and testosterone (T) were determined in bpl and spl, and in addition androstenedione (A), dehydroepiandrosterone (DHEA) and 5alpha-dihydrotestosterone (5alpha-DHT) were measured in spl. At certain points of time, aliquots of an ejaculate w...
Popot MA, Lacabaratz E, Garcia P, Laroute V, Bonnaire Y, Toutain PL, Cowan DA.The cortisol threshold concentration of 1.0 microg/ml in horse urine adopted by the International Federation of the racing Authorities in 1994 is specific. However, an increase in the sensitivity for the detection of cortisol administration would be helpful. Previous studies have shown that 20beta-dihydrocortisol concentration in urine would be a good indicator of cortisol administration. The purpose of the present work was to estimate the population parameters and the critical values of 20beta-dihydrocortisol and 20beta-dihydrocortisone concentration in urine compared with that of cortisol. U...
Watson ED, Thomson SR.Aromatase P-450 (P-450arom) is a crucial regulatory enzyme that is necessary for conversion of androgens to oestrogens. Corpora lutea and follicles were obtained from the ovaries of cyclic mares and from mares at day 20 and days 40-70 of pregnancy. The presence of P-450arom within specific cell types was investigated by immunostaining to determine potential sites of oestrogen synthesis. Immunoreactivity for P-450arom was confined to the granulosa layer of non-atretic follicles > 5 mm in diameter and to corpora lutea at all stages of the oestrous cycle and during pregnancy. These findings co...
Gerstenberg C, Allen WR.Branched tubular endometrial glands are key features of the uterine lining in mares. The epithelium in the neck regions of the glands is similar to that lining the lumen of the uterus, whereas the epithelium in the deeper, coiled portions of the glands secretes protein rich histotrophe or 'uterine milk' during dioestrus and pregnancy. The present study was performed to characterize endometrial histology in perinatal and peripubertal fillies and to investigate the influences of specific steroid treatments on endometrial gland development in the prepubertal period. Uteri obtained from equine fet...
Flood PF, Betteridge KJ, Irvine DS.Six samples of blastocoele fluid recovered between 10 and 22 days gestation were tested in human clinical radioimmunoassay systems measuring total oestrogens and total androgens. The results were erratic but in 5 cases measurements for oestrogen equivalent to between 1000 and 70,000 pg/ml and for androgen between 1000 and 85,000 pg/ml were recorded. Cells from two blastocysts were cultured in medium 199 with and without horse serum. When the used media were assayed, values equivalent to at least 8000 pg oestrogen/ml were obtained on 7 of 11 occasions. In 9 of 11 samples the androgen concentrat...
Weng Q, Tanaka Y, Taniyama H, Tsunoda N, Nambo Y, Watanabe G, Taya K.To elucidate the relationship between steroidogenic hormones and developing adrenal glands, we investigated the immunolocalization of steroidogenic enzymes in equine fetal adrenal glands during mid-late gestation. Fetal adrenal glands were obtained from three horses at 217, 225 and 235 days of gestation. Steroidogenic enzymes were immunolocalized using polyclonal antisera raised against bovine adrenal cholesterol side-chain cleavage cytochrome P450 (P450scc), human placental 3beta-hydroxysteroid dehydrogenase (3betaHSD), porcine testicular 17alpha-hydroxylase cytochrome P450 (P450c17) and huma...
Karatt TK, Sathiq MA, Laya S, Ajeebsanu MPM, Karakka Kal AK, Subhahar MB, Perwad Z.Recently, there has been a report suggesting that ecdysteroids can enhance sports performance, making them relevant substances in doping control. Hence, it is imperative to examine the analytical characteristics of ecdysteroids in biological samples to identify their misuse in competitive sports. Methods: To assess the doping of ecdysteroids such as ecdysone, ecdysterone, ponasterone A, turkesterone, and ajugasterone C, a fast and sensitive extraction and detection method was developed, optimized, and validated using equine urine and plasma. Different extraction techniques, namely, solid-phase...
Caprioli G, Genangeli M, Mustafa AM, Petrelli R, Ricciutelli M, Sagratini G, Sartori S, Laus F, Vittori S, Cortese M.A simple and fast analytical method able to simultaneously identify and quantify 17 endogenous and exogenous steroidal hormones was developed in bovine and equine blood using UHPLC-MS/MS. A total amount of 500 µL of sample was deproteinized with 500 µL of a mixture of methanol and zinc sulfate and evaporated. The mixture was reconstituted with 50 µL of a solution of 25% methanol and injected in the UHPLC-MS/MS triple quadrupole. The correlation coefficients of the calibration curves of the analyzed compounds were in the range of 0.9932-0.9999, and the limits of detection and quantification ...
Viljanto M, Kaabia Z, Taylor P, Muir T, Habershon-Butcher J, Bailly-Chouriberry L, Scarth J.Boldenone is an anabolic-androgenic steroid that is prohibited in equine sports. However, in certain situations, it is endogenous or is believed to be formed by microbes in urine, and therefore, an approach for the differentiation is required. Following the identification of Δ1-progesterone and 20(S)-hydroxy-Δ1-progesterone as potential biomarkers of microbial activity, the presence of six steroids was investigated in the postrace urine of castrated male horses (geldings, n = 158). In line with endogenous findings from several other species when ultrasensitive methods are employed, bolde...
Kirkpatrick JF, Shldeler SE, Lasley BL, Turner JW.This study was carried out to develop an accurate, rapid and inexpensive method for diagnosing pregnancy in uncaptured feral horses by analysis of fecal steroid metabolites and to compare the accuracy of this method with diagnosis by urinary estrone conjugates (E(1)C). Paired urine and fecal samples were collected from 40 sexually mature feral mares during August and October. Urine samples were extracted directly from the soil and analyzed by enzymeimmunoassay (EIA) for E(1)C. Water extracts of fecal samples were assayed by EIA for E(1)C and nonspecific progesterone metabolites (iPdG). Urinary...
You Y, Uboh CE, Soma LR, Guan F, Li X, Rudy JA, Liu Y, Chen J.An ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) method for fast-throughput analysis of eight anabolic and androgenic steroids (AAS) in equine plasma is reported. Analytes were recovered by liquid-liquid extraction using methyl tert-butyl ether, separated on a 1.9 microm C(18) reversed-phase column, and analyzed in positive electrospray ionization mode on a triple quadrupole mass spectrometer with selected reaction monitoring (SRM) and full product ion scans. Two SRM ion transitions were monitored for each AAS during screening to obtain highly selective screenin...
Brown KA, Boerboom D, Bouchard N, Doré M, Lussier JG, Sirois J.17Beta-hydroxysteroid dehydrogenase type 4 (17betaHSD4) has a unique multidomain structure, with one domain involved in 17beta-estradiol inactivation. The objective of the study was to investigate the regulation of 17betaHSD4 during human chorionic gonadotropin (hCG)-induced ovulation/luteinization. The equine 17betaHSD4 cDNA was cloned and was shown to encode a 735-amino acid protein that is highly conserved (81-87% identity) compared with other mammalian orthologs. RT-PCR/Southern blot analyses were performed to study the regulation of 17betaHSD4 transcripts in equine preovulatory follicles ...
Witt MC, Bollwein H, Probst J, Baackmann C, Squires EL, Sieme H.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 ...
Hosteller DE, Sprecher DJ, Yamini B, Ames NK.Transrectal palpation of an 18-mo-old, anestrous Holstein nulligravida revealed an enlarged left ovary. Ultrasonographically, the mass resembled known equine granulosa cell tumor (GCT) images. Slowly, virilism developed. Fifty-five days after initial diagnosis, unilateral ovariectomy was performed The presurgical serum concentration of testosterone was equal to that of a mature bull. During the 3 mo period following surgery, estrus expression resumed, the serum testosterone concentration returned to baseline, and the heifer was diagnosed pregnant following AI. A low grade, malignant GCT was th...
Gérard N, Monget P.The profiles of insulin-like growth factor-binding proteins (IGFBPs) in follicular fluid have been characterized in a number of mammals (rats, pigs, sheep, cattle, humans) and are good indicators of follicular status. We studied the IGFBP profiles of equine serum and ovarian follicular fluid recovered at various stages of the follicular phase. The levels of IGFBPs were related to the morphology and the steroidogenic activity of the follicles. Follicular fluids were recovered by ultrasound-guided follicular aspiration. In the first experiment, the dominant follicles of 10 mares were partly punc...
Teale P, Houghton E.The fight against doping in sport using analytical chemistry is a mature area with a history of approximately 100 years in horseracing. In common with human sport, anabolic/androgenic steroids (AASs) are an important group of potential doping agents. Particular issues with their detection are extensive metabolism including both phase I and phase II. A number of the common AASs are also endogenous to the equine. A further issue is the large number of synthetic steroids produced as pharmaceutical products or as 'designer' drugs intended to avoid detection or for the human supplement market. An u...
Waller CC, Weththasinghe SA, McClure L, Cawley AT, Suann C, Suann E, Sutherland E, Cooper E, Heather A, McLeod MD.Hemapolin (2α,3α-epithio-17α-methyl-5α-androstan-17β-ol) is a designer steroid that is an ingredient in several "dietary" and "nutritional" supplements available online. As an unusual chemical modification to the steroid A-ring could allow this compound to pass through antidoping screens undetected, the metabolism of hemapolin was investigated by an in vivo equine drug administration study coupled with GC-MS analysis. Following administration of synthetically prepared hemapolin to a thoroughbred horse, madol (17α-methyl-5α-androst-2-en-17β-ol), reduced and dihydroxylated madol (17α-me...
Raeside JI, Christie HL, Waelchli RO, Betteridge KJ.Estrogen production by the trophoblast is considered important in early equine pregnancy and leads to high concentrations in yolk-sac (Y-S) fluid. The embryo proper is a potential site for their action. We examined estrogen metabolism in the embryo proper because some actions of estrogens are derived from locally formed metabolites. The embryo proper, as well as separated extraembryonic tissues, of conceptuses collected about day 25 of pregnancy, were incubated with (3)[H]-estrone (E(1)) and (3)[H]-estradiol (E(2)). Steroids were recovered from media by solid-phase extraction and eluted separa...
Dehennin L, Bonnaire Y, Plou P.Dehydroepiandrosterone (DHEA) and androstenedione are weak androgens, which need conversion to more potent testosterone in order to enhance anabolic action. Consequences of oral dosing at 1 mg/kg on the urinary and plasma androgen profile of mare and gelding have been evaluated with an analytical method involving conjugate fractionation and selective hydrolysis, group separation, and quantitation by gas chromatography-mass spectrometry with selected ion monitoring of trimethylsilyl ethers. Peak levels of testosterone total conjugates in urine (range 300-6000 microg/L) were attained a few hours...
Irwin-Huston JM, Bourebaba L, Bourebaba N, Tomal A, Marycz K.Musculoskeletal injuries and chronic degenerative diseases pose significant challenges in equine health, impacting performance and overall well-being. Sex Hormone-Binding Globulin (SHBG) is a glycoprotein determining the bioavailability of sex hormones in the bloodstream, and exerting critical metabolic functions, thus impacting the homeostasis of many tissues including the bone. Unassigned: In this study, we investigated the potential role of SHBG in promoting osteogenesis and its underlying mechanisms in a model of equine adipose-derived stromal cells (ASCs). An SHBG-knocked down model has b...
Chang X, Zhang Z, Yao X, Meng J, Ren W, Zeng Y.The equine lipid metabolism is activated during and after endurance exercise to provide energy in response to the metabolic and physiological changes in the body caused by prolonged exercise; however, the specific regulatory mechanisms remain controversial and identifying differential lipid metabolites associated with equine endurance is essential to elucidate these regulatory mechanisms. In this study, blood samples for lipid metabolomic analysis and biochemical indices were collected before and after a 26 km race from 12 Yili horses with different endurance performance. The biochemical res...
Seamans MC, Roser JF, Linford RL, Liu IK, Hughes JP.Six normal stallions of light horse breeds aged 5-17 years were used from fall to winter to investigate the difference between steroid hormone concentrations in testicular and jugular venous blood before and after exogenous GnRH. At 48 h before experimentation, an indwelling cannula was placed surgically in the testicular vein of the stallion. After the stallion recovered from anaesthesia, a catheter was placed percutaneously in the jugular vein. Each stallion was housed in a tie stall to allow simultaneous sampling of jugular or testicular blood. On the first and second sampling days, respect...
Morris DD, Garcia MC.Adrenal and/or thyroid gland function tests were evaluated in horses at various times during short-term therapy with phenylbutazone, stanozolol, and boldenone undecylenate. There were no significant treatment or time effects on mean basal plasma cortisol concentrations in horses during treatment with the following: phenylbutazone, given twice daily (4 to 5 mg/kg, IV) for 5 days; stanozolol, given twice weekly (0.55 mg/kg, IM) for 12 days; boldenone undecylenate, given twice weekly (1.1 mg/kg, IM) for 12 days; or nothing. There was no significant effect of phenylbutazone treatment on the change...
Houghton E, Dumasia MC.1. The metabolism of 19-nor[4-14C]testosterone in a thoroughbred horse has been studied and neutral urinary metabolites obtained after enzyme hydrolysis have been investigated by g.l.c.-mass spectrometry. 2. 3-Hydroxyestran-17-one, 17 alpha- and 17 beta-nortestosterone, estrane-3,17-diol (two isomers), 3,16-dihydroxyestran-17-one (two isomers), 3,17-dihydroxyestran-16-one (two isomers) and estrane-3,16,17-triol were identified in the neutral urinary extracts.
Nett TM, Holtan DW, Estergreen VL.Levels of oestrone, equilin and equilenin (E1), oestradiol (E2) LH, PMSG and prolactin were measured by radioimmunoassay in serum from pregnant mares. Levels of E1 were always greater than those of E2. Both E1 and E2 remained at low levels until Day 80, increased significantly (P less than 0-05) by Day 120 to reach peak levels at Day 210 or 240 and then declined until parturition. Maximum levels of oestrogens observed in this study were 828 +/- 151 pg/ml for E1 and 71 +/- 18 pg/ml for E2 at Days 210 and 240 respectively. Spikes of LH release were observed in early pregnancy in most mares. Leve...
Slone DE, Purohit RC, Ganjam VK, Lowe JL.Three ponies and 1 horse were bilaterally adrenalectomized (BADX). The initial hypoadrenal episode after BADX was reversed with 20 mg of dexamethasone (DXM) IM (n = 2) or 20 mg of triamcinolone (TMC) IM (n = 2). Nine hypoadrenal crises were reversed with 20 mg of DXM given IM (n = 4) or 20 mg of TMC given IM (n = 5). Sodium and chloride retention and potassium excretion were documented based on changes in serum electrolytes and urinary excretion. Eight intact adult horses were randomly assigned to 2 groups to study the effects of a single IM injection of DXM (0.044 mg/kg of body weight) or TMC...
Alm YH, Sukjumlong S, Kindahl H, Dalin AM.Sex steroid hormone receptors have been identified in the adrenal gland of rat, sheep and rhesus monkey, indicating a direct effect of sex steroids on adrenal gland function. Methods: In the present study, immunohistochemistry using two different mouse monoclonal antibodies was employed to determine the presence of oestrogen receptor alpha (ERalpha) and progesterone receptor (PR) in the mare adrenal gland. Adrenal glands from intact (n = 5) and ovariectomised (OVX) (n = 5) mares, as well as uterine tissue (n = 9), were collected after euthanasia. Three of the OVX mares were treated with a sing...
