Cabrera P.; Aguila L.; Castro M,; Arias M. E. & Felmer R.

Frozen-thawed spermatozoa from different mammalian species successfully undergo capacitation in vitro under specific and defined conditions, however the induction of in vitro capacitation of equine spermatozoa still needs optimizations. The aim of this study was to evaluate the effects of different culture media on induction of in vitro capacitation of thawed stallion sperm. To do this, the sperm were thawed and incubated with different combinations of capacitating inducers for 2 h. In our study five different media: no capacitation medium (NC), basal medium that included BSA and bicarbonate, basal mediium plus capacitating inducer dibutyryl cyclic-AMP (dbcAMP) as a PKA activator, a phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) and a cholesterol acceptor, methyl-β-cyclodextrin (MβCD). The membrane fluidity, acrosome reaction and intracellular calcium levels were evaluated after 2 h of incubation, but we did not find any differences among groups. Different behavior between stallions was also observed. Finally, the sperm treatments were evaluated using a homologues zona pellucida binding assay. This assay showed that incubation in basal medium including MβCD increased the number of spermatozoa adhered to the zona pellucida of mare oocytes. Further studies are needed to evaluate the effect of these conditions on in vitro fertilization of equine species using thawed sperm.

KEY WORDS: Capacitation; Spermatozoa; Stallion; Zona pellucida.

CABRERA, P.; AGUILA, L.; CASTRO, M.; ARIAS, M. E. & FELMER, R. Capacitation inducers on thawed stallion sperm: Effect on sperm capacitation and homologous zona pellucida binding assay. Int. J. Morphol., 43(1):83-90, 2025.