Antioxidant treatment in the absence of exogenous lipids and proteins protects rhesus macaque sperm from cryopreservation-induced cell membrane damage

Osmotic stress caused oxidative stress in rhesus macaque sperm, which was alleviated by antioxidant supplementation. The objective of the present study was to demonstrate that cryopreservation of rhesus macaque sperm also induces reactive oxygen species (ROS) production, and to determine whether ROS have an important role in cryopreservation-induced membrane. Additionally, we evaluated the antioxidant capacity of TEST (N-Tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid-Tris) buffer (with 20% egg yolk and 13% skim milk) and supplementation with antioxidants, superoxide dismutase (SOD), catalase (CAT), and α-tocopherol. There was a substantial level of ROS production in both the presence (15% increase in superoxide, P < 0.01; 14% increase in hydrogen peroxide, P < 0.01) and absence of egg yolk (EY) and skim milk (SM; 33% increase in superoxide, P < 0.001; 48% increase in hydrogen peroxide, P < 0.001). Superoxide dismutase provided little membrane protection against ROS, but increased postthaw total and progressive motility by 10% (P < 0.01) and 15% (P < 0.05), respectively. Supplementation with CAT and α-tocopherol in the presence of EY and SM decreased H₂O₂ by 55% (P < 0.01) and 49% (P < 0.001), whereas supplementation with CAT and α-tocopherol in the absence of EY and SM reduced the level of lipid peroxidation by 61% (P < 0.05) and 28% (P < 0.01). In conclusion, this is apparently the first report that cryopreservation of rhesus macaque sperm induced a significant increase in ROS and that antioxidant supplementation (N-Tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid-Tris) can significantly decrease the extent of ROS-induced membrane damage.