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Journal of equine science2021; 32(2); 39-48; doi: 10.1294/jes.32.39

Circulating activin A during equine gestation and immunolocalization of its receptors system in utero-placental tissues and fetal gonads.

Abstract: Although equine gestation is unique from the standpoint of fetal gonadal enlargement and regression, the activator of this process is still unknown. The present study aimed to show a possible role of activin during equine gestation. In the first experiment, weekly plasma samples from six pregnant mares were used to measure activin A. In the second experiment, eight pregnant mares carrying female (gestational days 110, 140, 180, and 270) and male fetuses (gestational days 120, 180, 225, and 314) were used for immunohistochemistry of activin receptors (IA, IB, IIA, IIB), and their intracellular mediators (Smad2, Smad3, Smad4). Activin A levels in maternal circulation remained low until fourth weeks of gestation, thereafter, started to increase, and peaked first at 11 weeks of gestation. The second significant peak was observed on the day of parturition. Activin receptors type IA, IB, IIA, and IIB were immunostained in interstitial and germ cells of fetal ovaries and testes along with utero-placental tissues. Smad2, Smad3, and Smad4 were also immunolocalized in all these organs. These results demonstrated the activin-producing capacity of utero-placental tissues, and also evidenced the existence of activin receptors and functional signaling molecules in these organs. The first increment in circulating activin A in maternal circulation coinciding with the timing of initiation of fetal gonadal enlargement suggests that activin from the utero-placental tissues may have a stimulatory role in fetal gonad enlargement and utero-placental development in mares, whereas the second peak could be important to follicular development in the maternal ovary for foal heat.
©2021 The Japanese Society of Equine Science.
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Publication Date: 2021-06-18 PubMed ID: 34220270PubMed Central: PMC8240525DOI: 10.1294/jes.32.39Google Scholar: Lookup
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  • Journal Article

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 analyzes the role of a hormone called activin A in horse gestation, its presence in maternal circulation, and its receptors in utero-placental tissues and fetal gonads. There is evidence that activin A might stimulate fetal gonad enlargement and utero-placental development, with a secondary peak indicating a potential role in follicular development in the maternal ovary.

Objective of the Study

  • The study aims to shed light on the role of activin, a hormone, during horse pregnancy, focusing on its potential to activate fetal gonadal enlargement – a unique feature of equine gestation.

Study Methods

  • The study has two parts. In the first part, weekly blood samples were collected from six pregnant mares to measure the levels of activin A. The second part involved detecting the presence of activin receptors in pregnant mares carrying both female and male fetuses at different gestational stages, along with their intracellular mediators (Smad2, Smad3, Smad4).

Findings

  • The levels of activin A in the mother’s circulation system remained low until the fourth week of gestation, following which they started to increase, peaking first at around the eleventh week.
  • The second significant peak was observed on the day of birth, possibly indicating the involvement of activin A in follicular development in the mother’s ovary during foal heat (the first estrus after foaling). The study discovered activin receptors (IA, IB, IIA, IIB) holistically across the utero-placental tissues and in fetal ovaries and testes.
  • The study also acknowledges the presence of functional signaling molecules like Smad2, Smad3, and Smad4 in these same organs.

Outcome of Study

  • These results not only demonstrate that utero-placental tissues can produce activin but also confirm the existence of activin receptors and signaling molecules in these organs.
  • The first significant increase in circulating activin A coinciding with the point of fetal gonadal enlargement implies an activating role activin might have in this enlargement process and in the development of utero-placental tissues.
  • The study therefore suggests that activin potentially plays a part in the unique processes witnessed during horse pregnancy, specifically the enlargement and regression of fetal gonads.

Cite This Article

APA
Dhakal P, Tsunoda N, Nambo Y, Taniyama H, Nagaoka K, Watanabe G, Taya K. (2021). Circulating activin A during equine gestation and immunolocalization of its receptors system in utero-placental tissues and fetal gonads. J Equine Sci, 32(2), 39-48. https://doi.org/10.1294/jes.32.39

Publication

Journal of equine science
ISSN: 1340-3516
NlmUniqueID: 9503751
Country: Japan
Language: English
Volume: 32
Issue: 2
Pages: 39-48

Researcher Affiliations

Dhakal, Pramod
  • Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
  • Division of Animal Science, University of Missouri, MO 65211, U.S.A.
Tsunoda, Nobuo
  • Shadai Corporation, Hokkaido 059-1432, Japan.
Nambo, Yasuo
  • United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan.
  • Department of Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido 080-8555, Japan.
Taniyama, Hiroyuki
  • Department of Veterinary Pathology, Rakuno Gakuen University, Hokkaido 069-8501, Japan.
Nagaoka, Kentaro
  • Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
  • United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan.
  • Cooperative Division of Veterinary Sciences (Doctoral Program), Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
Watanabe, Gen
  • Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
  • United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan.
  • Cooperative Division of Veterinary Sciences (Doctoral Program), Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
Taya, Kazuyoshi
  • Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
  • Shadai Corporation, Hokkaido 059-1432, Japan.

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Citations

This article has been cited 1 times.
  1. Rişvanlı A, Kholmurzaevich AA, Sharabidinovich KA, Mamatkalykovych PM, Duyshobayeva A, Obdunov E, Yuksel BF, Turanlı M, Seker I, Eshimbekov T, Tynaibekovna RA. Single‑dose levamisole at breeding alters early pregnancy immune-endocrine profiles without affecting fertility in ewes. BMC Vet Res 2025 Sep 25;21(1):546.
    doi: 10.1186/s12917-025-04984-6pubmed: 40999486google scholar: lookup
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