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Equine fetal adrenal, gonadal and placental steroidogenesis.
Abstract: Equine fetuses have substantial circulating pregnenolone concentrations and thus have been postulated to provide significant substrate for placental 5α-reduced pregnane production, but the fetal site of pregnenolone synthesis remains unclear. The current studies investigated steroid concentrations in blood, adrenal glands, gonads and placenta from fetuses (4, 6, 9 and 10 months of gestational age (GA)), as well as tissue steroidogenic enzyme transcript levels. Pregnenolone and dehydroepiandrosterone (DHEA) were the most abundant steroids in fetal blood, pregnenolone was consistently higher but decreased progressively with GA. Tissue steroid concentrations generally paralleled those in serum with time. Adrenal and gonadal tissue pregnenolone concentrations were similar and 100-fold higher than those in allantochorion. DHEA was far higher in gonads than adrenals and progesterone was higher in adrenals than gonads. Androstenedione decreased with GA in adrenals but not in gonads. Transcript analysis generally supported these data. was higher in fetal gonads than adrenals or allantochorion, and was higher in fetal adrenals and allantochorion than gonads. transcript was also significantly higher in adrenals and gonads than allantochorion and and SRD5A1 transcripts were higher in allantochorion than either fetal adrenals or gonads. Given these data, and their much greater size, the fetal gonads are the source of DHEA and likely contribute more than fetal adrenal glands to circulating fetal pregnenolone concentrations. Low but high and transcript abundance in allantochorion, and low tissue pregnenolone, suggests that endogenous placental pregnenolone synthesis is low and likely contributes little to equine placental 5α-reduced pregnane secretion.
© 2017 Society for Reproduction and Fertility.
Publication Date: 2017-09-08 PubMed ID: 28878092DOI: 10.1530/REP-17-0239Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research article examines where pregnenolone, a hormone that contributes to the creation of other steroid hormones, is produced in equine fetuses. The study proposes that it may be the fetal gonads (sex organs), not the adrenal glands or placenta, that contribute significantly to circulating fetal pregnenolone concentrations.
Fetal Pregnenolone Production
- The research focuses on the origination of pregnenolone in equine fetuses as it wasn’t previously clear where this hormone was synthesized.
- Through investigations involving steroid concentrations in the blood, adrenal glands, gonads, and placenta of fetuses at different gestational ages (4, 6, 9 and 10 months), it was noted that pregnenolone and dehydroepiandrosterone (DHEA) are the most abundant steroids in fetal blood.
- Pregnenolone levels were found to be consistently higher, although they decreased as gestational age advanced.
Steroid Concentrations in Tissues
- Upon examining tissue steroid concentrations at different gestational ages, it was found that they generally paralleled those in the serum.
- Interestingly, adrenal and gonadal tissue pregnenolone concentrations were similar and 100-fold higher than those in the allantochorion, a part of the placenta.
- DHEA levels were observed to be much higher in the gonads than in the adrenal glands. In contrast, progesterone was found to be higher in the adrenal glands than the gonads.
- Transcript analysis, which underpins these data, reveals that the steroidogenic enzyme transcript levels to be higher in fetal gonads than in adrenals or allantochorion.
Role of Gonads and Adrenal Glands
- The research suggests that because of their much larger size, the gonads are likely the source of DHEA and contribute more significantly to circulating fetal pregnenolone concentrations than the adrenal glands.
- In terms of androstenedione, another steroid hormone, its level decreased with gestational age in adrenals but remained the same in the gonads.
Low Contribution from Placenta
- Contrary to previous postulates, the research suggests the placenta may contribute little to equine placental 5α-reduced pregnane secretion, as indicated by low placental tissue pregnenolone and high transcript abundance in the allantochorion.
In conclusion, the research sheds light on the complex process of steroidogenesis (production of steroid hormones) in equine fetuses, especially focusing on the significant role likely played by the gonads in circulating fetal pregnenolone concentrations. Also, it challenges the previous belief about the major role of the placenta in this process.
Cite This Article
APA
Legacki EL, Ball BA, Corbin CJ, Loux SC, Scoggin KE, Stanley SD, Conley AJ.
(2017).
Equine fetal adrenal, gonadal and placental steroidogenesis.
Reproduction, 154(4), 445-454.
https://doi.org/10.1530/REP-17-0239 Publication
Researcher Affiliations
- Department of Population Health and ReproductionSchool of Veterinary Medicine, University of California, Davis California, USA.
- Gluck Equine Research CenterDepartment of Veterinary Science, University of Kentucky, Lexington Kentucky, USA.
- Department of Population Health and ReproductionSchool of Veterinary Medicine, University of California, Davis California, USA.
- Gluck Equine Research CenterDepartment of Veterinary Science, University of Kentucky, Lexington Kentucky, USA.
- Gluck Equine Research CenterDepartment of Veterinary Science, University of Kentucky, Lexington Kentucky, USA.
- Department of Molecular BiosciencesSchool of Veterinary Medicine, University of California, Davis California, USA.
- Department of Population Health and ReproductionSchool of Veterinary Medicine, University of California, Davis California, USA ajconley@ucdavis.edu.
MeSH Terms
- 3-Oxo-5-alpha-Steroid 4-Dehydrogenase / genetics
- 3-Oxo-5-alpha-Steroid 4-Dehydrogenase / metabolism
- Adrenal Cortex Hormones / biosynthesis
- Adrenal Cortex Hormones / blood
- Adrenal Glands / embryology
- Adrenal Glands / metabolism
- Androstenedione / biosynthesis
- Androstenedione / blood
- Animals
- Aromatase / genetics
- Aromatase / metabolism
- Cholesterol Side-Chain Cleavage Enzyme / genetics
- Cholesterol Side-Chain Cleavage Enzyme / metabolism
- Dehydroepiandrosterone / biosynthesis
- Dehydroepiandrosterone / blood
- Embryo, Mammalian / metabolism
- Female
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Enzymologic
- Gestational Age
- Gonadal Steroid Hormones / biosynthesis
- Gonadal Steroid Hormones / blood
- Horses
- Male
- Multienzyme Complexes / genetics
- Multienzyme Complexes / metabolism
- Ovary / embryology
- Ovary / metabolism
- Placenta / embryology
- Placenta / metabolism
- Pregnancy
- Pregnenolone / biosynthesis
- Pregnenolone / blood
- Progesterone Reductase / genetics
- Progesterone Reductase / metabolism
- Steroid 17-alpha-Hydroxylase / genetics
- Steroid 17-alpha-Hydroxylase / metabolism
- Steroid Isomerases / genetics
- Steroid Isomerases / metabolism
- Testis / embryology
- Testis / metabolism
Citations
This article has been cited 16 times.- Boakari YL, Legacki E, Alonso MA, Dos Santos ACF, Nichi M, Conley AJ, Fernandes CB. Postnatal Dynamics of Circulating Steroid Hormones in Mule and Equine Neonates. Vet Sci 2022 Oct 28;9(11).
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- Lanci A, Mariella J, Ellero N, Faoro A, Peric T, Prandi A, Freccero F, Castagnetti C. Hair Cortisol and DHEA-S in Foals and Mares as a Retrospective Picture of Feto-Maternal Relationship under Physiological and Pathological Conditions. Animals (Basel) 2022 May 14;12(10).
- Gao Y, Hannan MA, Murata K, Rajabi-Toustani R, Nambo Y. Ultrasonographic examination of equine fetal growth parameters throughout gestation in pony for Equine-Assisted Therapy. J Vet Med Sci 2022 Jan 7;84(1):74-81.
- Scarlet D, Handschuh S, Reichart U, Podico G, Ellerbrock RE, Demyda-Peyrás S, Canisso IF, Walter I, Aurich C. Sexual Differentiation and Primordial Germ Cell Distribution in the Early Horse Fetus. Animals (Basel) 2021 Aug 17;11(8).
- Swink JM, Rings LM, Snyder HA, McAuley RC, Burns TA, Dembek KA, Gilsenan WF, Browne N, Toribio RE. Dynamics of androgens in healthy and hospitalized newborn foals. J Vet Intern Med 2021 Jan;35(1):538-549.
- Gabai G, Mongillo P, Giaretta E, Marinelli L. Do Dehydroepiandrosterone (DHEA) and Its Sulfate (DHEAS) Play a Role in the Stress Response in Domestic Animals?. Front Vet Sci 2020;7:588835.
- Loux SC, Dini P, El-Sheikh Ali H, Kalbfleisch T, Ball BA. Characterization of the placental transcriptome through mid to late gestation in the mare. PLoS One 2019;14(11):e0224497.
- Aleman M, McCue PM, Chigerwe M, Madigan JE. Plasma concentrations of steroid precursors, steroids, neuroactive steroids, and neurosteroids in healthy neonatal foals from birth to 7 days of age. J Vet Intern Med 2019 Sep;33(5):2286-2293.
- Arbogast DM, Metrione LC, Jones MK, Donelan EM, Roth TL, Freeman EW, Rispoli LA. Pregnancy- and age-associated variation in serum dehydroepiandrosterone concentrations in black and white rhinoceroses. Conserv Physiol 2026;14(1):coag007.
- Zamora-Sánchez CJ, González-Orozco JC, Mendoza-Ortega J, Villegas-Soto ML, Camacho-Arroyo I, Estrada-Gutierrez G. Neuroactive steroids in the programming of neurodevelopment: implications of maternal obesity. Front Endocrinol (Lausanne) 2025;16:1703103.
- de Lara NSS, Weiss RR, Oba E, Kozicki LE, Souza FA, Bergstein-Galan TG, Muehlbauer E, Silvestri M, de Lima PHL, Vaz ES. Prediction Values for the Influence of Fetal Sex on Plasma Progesterone Concentration in Crioulo Breed Mares: A Preliminary Investigation. Reprod Domest Anim 2025 Oct;60(10):e70131.
- Ellero N, Lanci A, Mariella J, van den Boom R, Cotticelli A, Peric T, Prandi A, Freccero F, Castagnetti C. Hair Allopregnanolone in Mares and Foals as a Retrospective Biomarker of Predicting Feto-Maternal Well-Being. Animals (Basel) 2025 Mar 7;15(6).
- Veronesi MC, Cotticelli A, Pividori I, Giombolini M, Corazzin M, Ellero L, Peric T. From Pre-Foaling to Late Pregnancy: Cortisol, DHEA(S), Progesterone, 17-β-Estradiol, and Allopregnanolone Hair Concentration Profiles in Standardbred Mares. Animals (Basel) 2025 Jan 23;15(3).
- Rouge M, Legendre F, Elkhatib R, Delalande C, Cognié J, Reigner F, Barrière P, Deleuze S, Hanoux V, Galéra P, Bouraïma-Lelong H. Early Castration in Horses Does Not Impact Osteoarticular Metabolism. Int J Mol Sci 2023 Nov 26;24(23).
- Roy S, Roy S, Mahata B, Pramanik J, Hennrich ML, Gavin AC, Teichmann SA. CLICK-chemoproteomics and molecular dynamics simulation reveals pregnenolone targets and their binding conformations in Th2 cells. Front Immunol 2023;14:1229703.
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