Effects of sodium pyruvate on viability, synthesis of reactive oxygen species, lipid peroxidation and DNA integrity of cryopreserved bovine sperm.

The aim of this study was to examine effects of sodium pyruvate on viability as well as on synthesis of reactive oxygen species (ROS), lipid peroxidation and DNA integrity of cryopreserved bovine sperm. In each of 23 Simmental AI bulls three ejaculates were collected. In a split sample design ejaculates were diluted by using Triladyl® extender without and with the addition of 5mM sodium pyruvate. Both aliquots were equilibrated for 24h before freezing. Frozen sperm samples were thawed, and examined immediately after thawing (0h) as well as after 3, 6, 12, and 24h incubation at 37°C. The percentages of rapidly motile sperm (RMS), plasma membrane and acrosome intact sperm (PMAI), sperm with a high mitochondrial membrane potential (HMMP), amounts of ROS synthesis (dichlorofluorescein-diacetate (DCFH), CellROX Deep Red Reagent® probe (CellROX)) and lipid peroxidation of sperm (LPO) and percentage of sperm with a high degree of DNA fragmentation (%DFI) were determined. Overall, sperm diluted with the extender containing sodium pyruvate showed higher levels of RMS, PMAI and HMMP, CellROX and lower %DFI values (P<0.001) compared to sperm frozen in the extender without sodium pyruvate. However, there was no effect (P>0.05) of sodium pyruvate on LPO and DCFH. The results of this study show that the addition of sodium pyruvate to the semen extender improved the viability as well as DNA integrity of cryopreserved sperm and did not affect their lipid peroxidation, although it increased the synthesis of some ROS.