Effect of sex sorting on stallion spermatozoa: Heterologous oocyte binding, tyrosine phosphorylation and acrosome reaction assay

The interest on sex sorting by flow cytometry on the equine industry has been increasing over the years. In this work, three different tests were performed in order to evaluate the membrane status of sorted stallion spermatozoa: assessment of binding ability to porcine oocytes, evaluation of acrosome integrity after stimulation with A23187, and detection of tyrosine phosphorylation. These evaluations were made after incubation for 0 h, 1.5 h and 3 h in a capacitating medium. Sorted stallion spermatozoa attached similarly to the porcine oocytes, when compared with control samples. Sorted spermatozoa were more prone to undergo acrosome reaction (P < 0.05), at the beginning and after 1.5 h and 3 h of incubation, and also had higher tyrosine phosphorylation of the tail (P < 0.001), only at the beginning of the incubation period. Apparently sex sorted stallion spermatozoa are in a more advanced status of membrane destabilization, which could be associated with capacitation, although similar binding ability to porcine oocytes is maintained.