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.

Determination of the proper time for mating after oestrous synchronisation during anoestrous or oestrous by measuring electrical resistance of cervical mucus in ewes

“…Taking the above into account, ewes that conceived might be mated before the LH surge and at the beginning of oestrus, whilst those that did not conceive may be mated late in oestrus. In addition, changes in progesterone concentrations in the genital tract could influence sperm capacitation (Barboni et al 1995), acrosome reaction (Cheng et al 1998) and probably sperm motility and chemoattraction. Thus, with respect to all these observations, the increased progesterone concentrations in the ewes that did not conceive might have negatively affected spermatozoa (capacitation or acrosome reaction), directly or indirectly via alterations in ERCM.…”

EFECTO DEL FLUIDO FOLICULAR SOBRE LA CAPACIDAD DE UNIÓN A ZONA PELÚCIDA DE ESPERMATOZOIDES EPIDIDIMARIOS DE ALPACA (Vicugna pacos)

“…Anteriormente, se ha podido reconocer para otras especies que el fluido folicular favorece ciertas funciones asociadas con la capacidad fecundante como la movilidad y la reacción acrosomal (Yanagimachi, 1969;Tesarík, 1985;Suarez et al, 1986;Morales et al, 1989;Ravnik et al, 1990;Hansen et al, 1991;McNutt y Killian, 1991;Ravnik et al, 1992;McNutt et al, 1994;Cheng et al, 1998;Jeon et al, 2001;Thérien et al, 2001;Briton-Jones et al, 2001;Schuffner et al, 2002;Getpook y Wirotkarun, 2007;Esmaeilpour et al, 2014;Leemans et al, 2015). Estudios previos en nuestro laboratorio determinaron que el fluido folicular favorece la movilidad espermática en alpaca (Bravo y Valdivia, 2017).…”

Capacitation, acrosome function and chromatin structure in stallion sperm

“…Physiological inducers of the AR are still under study but it is believed that, as well as ZP, several components of ovarian follicular fluid come into this category (Bruker and Lipford, 1995). In the horse, follicular fluid has been shown to induce the AR in pre-incubated stallion spermatozoa, and progesterone was found to be involved in this process (Cheng et al, 1998a;Rathi et al, 2003). Indeed, it appears that progesterone enhances both sperm-ZP binding and ZP-mediated induction of the AR via specific receptors on the plasma membrane (Cheng et al, 1998b).…”