Detection of Androgen Receptors in Spermatozoa of Small Ruminants: A Putative Modulation Pathway for Cryoresistance Through AQP3

Abstract

This work was aimed to identify androgen receptors (AR) in the spermatozoa of wild and domestic ruminants and to assess the effect of testosterone on sperm localization of aquaporin-3 (AQP3) and cryopreservation process. Sperm samples from wild species were incubated with testosterone (T group), 1,3-propanediol (PDO group), phloretin (PHL group), PDO+T group, PHL+T group. Western blot identified the presence of AR as a single band of about 48 KDa. Immunolabelling of AR was located in the equatorial segment of the sperm head. In mouflons, the cryoresistance ratio for acrosome integrity was lower (p < 0.05) in the PHL+T than in Control and T groups. In ibexes, the cryoresistance ratio for acrosome integrity was lower (p < 0.05) in the PHL+T, PHL, and T group than in the Control group; the cryoresistance ratios for sperm kinematic variables were lower (p < 0.05) in PDO+T than in Control. No changes were found among treatments in the proportion of spermatozoa showing AQP3 in the different membrane domains after incubation and thawing in both mouflon and ibex. In conclusion, testosterone negatively affected sperm cryoresistance expressed as acrosome integrity, enhancing the effects of the AQP blocker PHL. Our findings provide a sound knowledge of the molecular mechanisms that explain the seasonal variation in sperm freezability from ruminants.