Superoxide dismutase (SOD) is an antioxidant enzyme that attenuates cell oxidative stress by catalyzing the dismutation of superoxide anion (O2-) to hydrogen peroxide (H2O2) and water. The aim of this study was to evaluate the relationship of SOD activity in boar seminal plasma (SP) with the quality and sperm functionality of semen artificial insemination (AI) doses stored up to 72 h at 17°C. Boar ejaculates (11 boars, four ejaculates per boar) were split into two aliquots: collection of sperm free SP samples by centrifugation (twice at 1,500 x g for 10 min) and an aliquot for extension, using a commercial extender, to 30 x 106 sperm/mL (standard commercial AI-dose) and stored at 17 °C for up to 72 h. The SOD activity was measured in each SP-sample using a commercially available kit (RANSOD kit, RANDOX Laboratories Ltd, Crumlin, UK) and an automated analyzer (AU 600, Olympus, Maple Grove, MN, USA). Sperm quality and functionality were assessed at 0 and 72 h of liquid storage. Sperm motility was evaluated by CASA (ISASV1®, Proiser R+D, Valencia, Spain). Viable sperm with intact acrosome (H-42, PI and FITC-PNA) and generation of intracellular H2O2 in viable sperm (H-42, PI and CM-H2DCFDA) were evaluated by flow cytometry (BD FACSCanto II, Becton, Dickinson, CA, USA). The 44 ejaculates were classified (hierarchical clustering; P < 0.001) into 2 groups as with low (from 1.00 to 3.26 IU/mL; n = 20) or high (from 3.6 to 5.69 IU/mL; n = 24) SP-SOD activity. The ejaculates at 72 h with high SP-SOD activity showed higher percentage of total (P < 0.05) and progressive sperm (P < 0.001) motility (75.46 ± 2.24 and 47.46 ± 2.37, respectively) than those with low SP-SOD activity (59.95 ± 6.21 and 28.35 ± 2.92, respectively). Similarly, the ejaculates with high SP-SOD activity showed higher intracellular H2O2 generation (mean arbitrary fluorescence intensity was 15.79 ± 1.21 FU × 106 viable sperm) than those with low SP-SOD activity (12.22 ± 1.05 FU × 106 viable sperm). In conclusion, a high SOD activity in SP attenuates oxidative stress and improves sperm motility in pig semen liquid stored AI-doses.
Acknowledgement: Supported by MINECO (AGL2015-69738-R), Madrid, Spain and FEDER Funds (EU).