Effect of monosaccharides in glycerol-free tris extender on reactive oxygen species and apoptosis in dog sperm cryopreservation

BACKGROUND OBJECTIVE: The present study investigated the effect of monosaccharides in a glycerol-free tris (GFT) extender on reactive oxygen species (ROS) levels and apoptosis in cryopreserved dog spermatozoa. MATERIALS AND METHODS: The sperm pellets were resuspended (5 × 10⁷ mL^-1) with GFT containing 172 mM glucose (G), 86 mM glucose + 86 mM fructose (GF), 86 mM glucose + 86 mM galactose (Gg), 172 mM fructose (F), 172 mM galactose (g) or 86 mM fructose + 86 mM galactose (Fg). The sperm (500 µL) were loaded in 0.5 mL straws and cooled for 50 min at 4°C. The straws were then frozen 7 cm from the surface of liquid nitrogen (LN₂) for 20 min and were finally plunged into LN₂. After freezing-thawing, the sperm motility and viability were evaluated. The ROS level (H₂O₂) and apoptosis index were assessed by using flow cytometry. RESULTS: GFT supplemented with GF resulted in significantly higher (P < 0.05) progressive sperm motility and viability followed by only G, which had greater ROS reducing capacity. However, sperm cell apoptosis had no significant differences among all the experimental groups. CONCLUSION: Cryopreservation of dog sperm in GFT containing GF yields more motile and viable sperm followed by only G, which has greater ROS reducing efficiency.