The influence of cryoprotectants on sturgeon (Acipenser ruthenus) sperm quality, DNA integrity, antioxidant responses, and resistance to oxidative stress

• Thawed sturgeon sperm is dependent on the cryoprotectant used.
• Ethylene glycol combined with the xanthine–xanthine oxidase system causes toxicity in cellular systems.
• Ethylene glycol- and dimethylacetamide-cryopreserved sperm showed highly increased levels of superoxide dismutase and glutathione reductase.
• Chemical nature of dimethylacetamide makes post-thaw spermatozoa more susceptible to reactive oxygen species.
• Cryopreserved sperm with 10% methanol showed the highest resistance to oxidative stress.

This study examined the effect of cryoprotectants on DNA integrity, antioxidant defense, and resistance to oxidative stress in cryopreserved sterlet Acipenser ruthenus sperm. The freeze-thaw process significantly influenced sperm motility, with significant differences among cryoprotectants. In vitro exposure of cryopreserved sperm to the xanthine–xanthine oxidase (X–XO) system as a model reactive oxygen species inducer resulted in a lesser motility rate and velocity compared to the control, and there was a decrease in these variables in a time- and dose-dependent manner. The greatest X (0.6 mM)–XO (0.05 U/mL) concentration and incubation period (30 min) was associated with 62% DNA fragmentation in sperm cryopreserved with 10% ethylene glycol (EG). The maximum lipid peroxidation (LPO) and carbonyl derivatives of proteins (CP) was also observed in sperm cryopreserved with 10% EG and exposed to the X–XO system at a concentration of 0.6 mM X–0.05 U/mL XO. The frozen/thawed sperm containing 10% EG and that with 10% dimethyl sulfoxide (DMSO) had a significant enhancement of superoxide dismutase (SOD) and glutathione reductase (GR) activity. The current study confirms that EG is not effective for cryopreservation, and sterlet sperm were highly sensitive to free radicals after cryopreservation with EG.