Effect of oxytocin, prostaglandin F2 alpha, and clenbuterol on uterine dynamics in mares.
Abstract: The effects of oxytocin, prostaglandin F2 alpha (PGF2 alpha), and clenbuterol on uterine contractility and tone during anestrus and diestrus, and during mobility and postfixation of the embryonic vesicle were studied in 51 pony mares. Contractility was assessed by scoring real-time ultrasound images, and tone was assessed by transrectal digital compression. Scoring was done by an operator who had no knowledge of treatment assignments. In anovulatory mares primed with progesterone for 16 d, oxytocin did not significantly alter contractility but did stimulate an increase in tone, whereas clenbuterol depressed both contractility and tone. The PGF2 alpha given on Days 12, 15, and 18 did not significantly alter uterine contractility in pregnant mares, but it increased contractility on all days in nonpregnant mares. Clenbuterol decreased both tone and contractility when given to pregnant mares on the day of embryonic-vesicle fixation, while it decreased tone but not contractility when given on Day 19. Clenbuterol treatment was associated with dislodgment of the fixed embryo in only 1 of 5 mares. However, on Day 19, clenbuterol treatment was associated with a change in shape of the conceptus when viewed in a cross section of the uterine horn. The conceptus shape became more circular rather than irregular or triangular, as indicated by a significant decrease in the variation in the distances between adjacent walls measured in 4 different directions. Results indicated that: 1) oxytocin increased uterine tone but did not alter contractility in progesterone-primed anestrous mares; 2) on Days 12, 15 and 18, PGF2 alpha increased uterine contractility in nonpregnant mares but not in pregnant mares; 3) clenbuterol decreased both tone and contractility at all reproductive states except for a lack of a decrease in contractility on Day 19 of pregnancy; and 4) reduction in uterine tone from clenbuterol treatment on Day 19 was associated with a change in the two-dimensional shape of the in situ conceptus from irregular to a more circular form.
Publication Date: 2000-03-25 PubMed ID: 10732144DOI: 10.1016/s0093-691x(98)00158-7Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research discusses the impact of three separate substances – oxytocin, prostaglandin F2 alpha (PGF2 alpha), and clenbuterol – on the uterine dynamics of mares, with particular emphasis on contractility and tone in varying stages of reproduction and pregnancy.
Overview of Study Methods and Design
- The study was conducted on 51 pony mares, using real-time ultrasound imaging and transrectal digital compression to assess uterine contractility and tone respectively.
- The mares were at different stages of their reproductive cycles: anestrus (non-reproductive period), diestrus (the period between two estrous cycles), and different phases of embryo fixation.
- The outcome scoring was carried out by a blinded operator, thus eliminating potential bias.
- Anovulatory (non-ovulation) mares were treated with progesterone for 16 days to study the effects of the substances.
Findings Pertaining to Oxytocin
- Oxytocin was found to increase the uterine tone, while not resulting in significant changes to contractility in mares stimulated with progesterone during anestrus.
Findings Pertaining to PGF2 Alpha
- Administration of PGF2 alpha on Days 12, 15, and 18 did not impact the uterine contractility in pregnant mares, but exhibited increased contractility in nonpregnant mares on these days.
Findings Pertaining to Clenbuterol
- Clenbuterol was seen to depress both contractility and tone. On the day of embryonic-vesicle fixation in a pregnant mare, clenbuterol decreased both tone and contractility, while on Day 19, it reduced the tone without impacting contractility.
- Interestingly, only one instance of embryonic displacement was noted with clenbuterol treatment. However, clenbuterol introduced changes to the two-dimensional shape of the in utero conceptus (embryo and its associated membranes), making it more circular than the usual irregular or triangular shape, notably on Day 19.
Conclusion
- The results demonstrate varied effects on uterine dynamics based on the substance applied and the stage of reproduction.
- The potential influence of these substances on reproductive health and pregnancy in mares warrants further study.
Cite This Article
APA
Gastal MO, Gastal EL, Torres CA, Ginther OJ.
(2000).
Effect of oxytocin, prostaglandin F2 alpha, and clenbuterol on uterine dynamics in mares.
Theriogenology, 50(4), 521-534.
https://doi.org/10.1016/s0093-691x(98)00158-7 Publication
Researcher Affiliations
- University of Wisconsin, Madison 53706, USA.
MeSH Terms
- Animals
- Clenbuterol / pharmacology
- Dinoprost / pharmacology
- Female
- Horses / physiology
- Kinetics
- Oxytocin / pharmacology
- Pregnancy
- Progesterone / pharmacology
- Uterine Contraction / drug effects
- Uterine Contraction / physiology
Citations
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