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Source of oestrogen in early pregnancy in the mare.
Abstract: Oestrogen secretion was determined by oestrogen conjugate (EC) analysis of urine in three groups of pregnant mares: Group I (N = 6), animals ovariectomized on Day 18-19 of gestation with pregnancy maintained by daily administration of an oral progestagen, altrenogest; Group II (N = 9), untreated, pregnant mares; Group III (N = 5) intact, pregnant mares treated daily with altrenogest. The mean EC concentrations in the ovariectomized mares in Group I increased in a constant linear manner from 17 ng/mg Cr on Day 20 to 291 ng/mg Cr on Day 70, with no apparent surge in oestrogen secretion around Day 39. Mean EC concentrations on Days 33, 39 and 44 were respectively 41, 48, and 73 ng/mg Cr. In the intact mares in Groups II and III (shown in parentheses), the mean urinary EC concentrations were 201 (171) ng/mg Cr between Days 20 and 33 of gestation, increased rapidly from 172 (77) ng/mg Cr on Day 33 to a peak of 1066 (895) ng/mg Cr on Day 39, followed by a decline to 637 (719) ng/mg Cr on Day 44. After Day 44, EC concentrations continued to increase in a linear manner to 1191 (842) ng/mg Cr on Day 70. The mean EC concentrations between Days 20 and 70 in Group I were significantly (P less than 0.05) lower than in mares in Groups II and III. EC concentrations in Group III mares were significantly lower (P less than 0.05) than in Group II mares between Days 28 and 34.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1990-09-01 PubMed ID: 2172534DOI: 10.1530/jrf.0.0900055Google 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.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study explores oestrogen secretion in early pregnancy in mares, using three different groups of pregnant mares under different conditions to understand the source of this hormone.
Research Study Groups
In the study, researchers observed three distinct groups of pregnant mares:
- Group I: Six mares that had been ovariectomized (ovaries removed) on Day 18-19 of gestation and whose pregnancies were sustained by a daily oral progestagen, altrenogest.
- Group II: Nine untreated, pregnant mares.
- Group III: Five intact, pregnant mares treated daily with altrenogest.
Methodology and Observations
Oestrogen secretion was determined by analysing oestrogen conjugate (EC) in the urine of the mares. The EC concentrations were examined and compared across the three groups at different gestation stages.
- In Group I, researchers noticed a steady linear increase in mean EC concentrations from 17 ng/mg Cr on Day 20 to 291 ng/mg Cr on Day 70, without an observable surge in oestrogen secretion on about Day 39.
- However, the intact mares in Groups II and III showed different results. Between Days 20 and 33 of gestation, mean urinary EC concentrations rose quickly from 172 (77) ng/mg Cr on Day 33 to a peak of 1066 (895) ng/mg Cr on Day 39, followed by a decrease to 637 (719) ng/mg Cr on Day 44. After Day 44, EC concentrations continued to increase in a linear way, reaching 1191 (842) ng/mg Cr on Day 70.
Conclusion
Overall, the study found a significant difference in oestrogen secretion between ovariectomized mares and intact mares either untreated or treated with altrenogest. The intact mares showed a rapid increase and then decline of EC concentrations around Day 39, followed by a continued linear increase; however, ovariectomized mares displayed a consistent linear growth without any surge.
This study suggests that the ovaries play a role in the surge of oestrogen secretion around Day 39 of gestation in pregnant mares. However, even when the ovaries are removed, oestrogen continues to steadily increase, suggesting that other sources also contribute to oestrogen secretion in pregnant mares.
Cite This Article
APA
Daels PF, Shideler S, Lasley BL, Hughes JP, Stabenfeldt GH.
(1990).
Source of oestrogen in early pregnancy in the mare.
J Reprod Fertil, 90(1), 55-61.
https://doi.org/10.1530/jrf.0.0900055 Publication
Researcher Affiliations
- Department of Reproduction, School of Veterinary Medicine, University of California, Davis 95616.
MeSH Terms
- Animals
- Estrogens / biosynthesis
- Estrogens, Conjugated (USP) / urine
- Female
- Horses / metabolism
- Horses / urine
- Ovariectomy
- Ovary / metabolism
- Pregnancy
- Pregnancy, Animal / urine
Citations
This article has been cited 2 times.- Haneda S, Dini P, Esteller-Vico A, Scoggin KE, Squires EL, Troedsson MH, Daels P, Nambo Y, Ball BA. Estrogens Regulate Placental Angiogenesis in Horses. Int J Mol Sci 2021 Nov 9;22(22).
- Oda K, Yoshida M, Irshad AR, Kanazawa T, Takahashi T. Development of a fluorometric Cuboni test for the semi-quantitative measurement of urinary estrogen levels and pregnancy detection in mares. J Reprod Dev 2024 Feb 19;70(1):25-29.
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