Cooling storage of ram sperm in presence of antioxidant glutathione

In the process of cryopreservation, the semen of farm animals can be threatened by many factors, such as oxidative damage, which affect the motility and plasma membrane function of the sperm. As an endogenous antioxidant in animals, glutathione (GSH) can significantly improve the quality of thawed sperm when added to the diluent of the semen. This study was aimed at examining the effect of GSH (given at 0.5 mM, 1.5 mM and 5 mM) on the motility and viability of ram sperm following storage under cooling conditions for several days. GSH reduced the negative effect of the cooling conditions on the total and progressive motility (CASA), stability of the membranes (annexin V/PI) and incidence of the apoptosis/necrosis (Yo-Pro-1/PI) in the sperm maintained at 5 °C for 24 h and 48 hours. However, this effect was neither reflected in the penetrating nor in the fertilising ability (zygotic cleavage rate) of the sperm examined in a heterologous (bovine oocytes and ram sperm) in vitro fertilisation test with GSH applied at 1.5 mM for 48 h of cooling storage. These results indicate that the addition of GSH to the sperm extender can maintain the quality of the ram sperm stored at cooling conditions for at least two days. To make a definite conclusion about the GSH effect on the sperm functionality (fertilising ability), other GSH concentrations should be tested.