SECRETIONS OF OVINE UTERUS AND OVIDUCT INDUCE IN-VITRO CAPACITATION OF RAM SPERMATOZOA

Interaction between spermatozoa and female reproductive tract fluids i nvolves both losses of surface proteins and adsorption of exogenous fl uids' components. To study the functional consequences of this interac tion, sperm acrosome reaction was evaluated after incubation at 37 deg rees C in uterine (UF) and/or oviductal (OF) fluid collected at estrus from conscious ewes. Ram spermatozoa were collected through the cathe terized vas deferens. The fluids had previously been diluted with equa l volumes of BWW medium or dialyzed against BWW. Control incubations w ere in BWW. Twenty minutes before the end of incubation, Ca2+ (2.5 mM) was added to induce the acrosome reaction, which was assessed using a triple stain technique. Results showed that 22-24% of the sperm exper ienced acrosome reaction after sequential incubation in UF (1 h) and O F (4 h), or in UF alone (5 h). Exposure to OF alone induced 13% of acr osome reaction. When the spermatozoa were preincubated in UF followed by OF, the acrosome reaction percentage increased almost linearly with time. When incubated in UF alone, this percentage increased steadily with time, whereas a plateau was reached after 1 h of incubation in OF alone. Dialysis of the fluids did not modify the results. These resul ts show that ewe reproductive tract secretions may capacitate ram sper matozoa in vitro, evaluated by their efficacy to induce acrosome react ion.