Progesterone in mare follicular fluid induces the acrosome reaction in stallion spermatozoa and enhances in vitro binding to the zona pellucida.
Abstract: The aim of this study was to investigate whether mare follicular fluid (FF) induces the acrosome reaction (AR) in stallion spermatozoa and, if so, to identify the component in FF responsible for it. Furthermore, the effect of this component on sperm-zona binding and the subsequent AR was studied. Pooled FF, aspirated from the preovulatory follicles of mares in oestrous, was used and aliquots of the fluid were treated with charcoal to remove steroids (CFF). Charcoal treatment reduced the progesterone concentration in FF from 153 to < 2 ng/mL. Spermatozoa from fertile stallions collected by a swim-up procedure were preincubated in modified Tyrode's medium for 5 h and then incubated for 30 min at 37 degrees C with either (1) 50% FF + 50% CFF, (2) 50% FF + 50% CFF + 150 ng/mL progesterone, (3) 50% CFF + 150 ng/mL progesterone, (4)150 ng/mL progesterone or (5) modified Tyrode's medium alone. The sperm-hemizona assay was applied: (a) to compare the number of spermatozoa bound to a hemizona in the presence and absence of 1.5, 15 or 150 ng/mL progesterone after 1 h co-incubation of spermatozoa and hemizonae, (b) to compare the incidence of the AR in sperm-hemizona complexes incubated for 1 h in the presence and absence of 1 microgram/mL progesterone. Both spermatozoa in suspension and bound to a hemizona were treated with the supravital dye Ethidium homodimer and fixed. Their plasma membranes were permeabilized, and the outer acrosomal membranes were labelled with FITC-PNA. Viable spermatozoa without the outer acrosomal membrane were considered as physiologically acrosome-reacted. Results showed that (1) FF induced a higher percentage of AR than did CFF or modified Tyrode's medium, (2) addition of 150 ng/mL progesterone to CFF restored 77% of the AR-inducing activity and (3) CFF and modified Tyrode's medium both induced the AR to a similar extent when supplemented with 150 ng/mL progesterone. Neither FF nor progesterone treatment affected sperm viability severely. The number of spermatozoa bound to a hemizona in the presence of 15 and 150 ng/mL progesterone was significantly higher (p < 0.05) than the number of spermatozoa bound in the absence of progesterone. A higher incidence of the AR was found in sperm-hemizona complexes incubated in the presence of progesterone (55.6 +/- 3.4% vs. 27.1 +/- 4.3%, in the presence and absence of progesterone, respectively) (n = 15, p < 0.05). It is concluded that mare FF can induce the AR in stallion spermatozoa. Progesterone is the physiological component responsible for this AR-inducing capacity. Progesterone enhances sperm-zona binding activity and exerts an additive effect on the zona-induced AR.
Publication Date: 1998-07-24 PubMed ID: 9675614DOI: 10.1046/j.1365-2605.1998.00096.xGoogle Scholar: Lookup
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Summary
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This research study investigates if the follicular fluid found in mares can induce an acrosome reaction in stallion sperm and identifies the key component causing this. The study reveals that progesterone, a hormone commonly found in the follicular fluid, sparks this reaction and enhances the binding of sperm to the zona pellucida, important for successful fertilization.
Research objectives and method
- The primary objective of this study was to explore if follicular fluid (FF), a fluid that fills ovarian follicles, from mares could stimulate an acrosome reaction (AR) – a crucial physiological process for fertilization – in stallion sperm.
- Another aim was to identify the specific component in the FF responsible for triggering the AR.
- The researchers also assessed the effect of this component on the sperm’s ability to bind to the zona pellucida (outer covering of an egg) and on the subsequent acrosome reaction.
- The researchers took FF from preovulatory follicles of mares in heat and treated some of this fluid with charcoal to remove steroids, creating a sample known as charcoal-treated follicular fluid (CFF).
- The stallion sperm used in the investigation was gathered using a swim-up procedure, where the most mobile sperm swim up into fresh medium
- The sperm was pre-incubated in a modified version of Tyrode’s medium, a solution often used in biological research, before being treated with various concentrations of FF, CFF, and progesterone.
Testing and interpretation of results
- Utilizing the sperm-hemizona assay, the researchers compared the number of sperm binding to a hemizona (half of a zona pellucida) and the incidence of the AR, with varying levels of progesterone present.
- Both free-floating sperm and sperm attached to a hemizona were procured, labelled, and treated to reveal if an acrosome reaction had occurred.
- The results showed that the FF caused a higher percentage of AR in the sperm compared to the CFF or the modified Tyrode’s medium.
- It was also observed that when 150 ng/mL progesterone was added to CFF, 77% of the AR-inducing effect was recovered.
- The number of sperm binding to a hemizona was significantly larger when 15 and 150 ng/mL progesterone was present, compared to when no progesterone was present.
- A higher frequency of AR occurred in sperm-hemizona combinations when progesterone was present compared to when it was absent.
Conclusions
- The study concluded that the FF in mares can indeed induce an acrosome reaction in stallion sperm.
- The hormone progesterone was identified as the physiological component in FF that is responsible for inducing the AR.
- It was also noted that progesterone enhances the ability of the sperm to bind to the zona pellucida and therefore increases the likelihood of successful fertilization.
Cite This Article
APA
Cheng FP, Fazeli AR, Voorhout WF, Tremoleda JL, Bevers MM, Colenbrander B.
(1998).
Progesterone in mare follicular fluid induces the acrosome reaction in stallion spermatozoa and enhances in vitro binding to the zona pellucida.
Int J Androl, 21(2), 57-66.
https://doi.org/10.1046/j.1365-2605.1998.00096.x Publication
Researcher Affiliations
- Department of Herd Health & Reproduction, Veterinary Faculty, Utrecht University, The Netherlands.
MeSH Terms
- Acrosome / physiology
- Animals
- Female
- Follicular Fluid / physiology
- Horses
- In Vitro Techniques
- Male
- Progesterone / physiology
- Sperm-Ovum Interactions
- Spermatozoa / physiology
- Spermatozoa / ultrastructure
- Zona Pellucida / physiology
Citations
This article has been cited 1 times.- Orsolini MF, Meyers SA, Dini P. An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section I.. Animals (Basel) 2021 Nov 13;11(11).
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