TEMPOL improves the post-thaw sperm quality in Zhikong scallops Chlamys farreri

Previous study demonstrated that the post-thaw sperm performance was significantly affected by the disturbance of antioxidant defense system due to the overproduction of reactive oxygen species (ROS). The present study examined whether such a disturbance could be mitigated by the addition of compounds with direct or indirect antioxidant properties into 6% dimethyl sulfoxide (DMSO), the optimal cryoprotectant solution published for Zhikong scallop Chlamys farreri sperm. The results showed that in comparison with 6% DMSO, the supplementation of 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) at 50 μM could reduce the sperm to egg ratio by 25% to achieve a fertilization rate comparable to that of fresh control. In contrast, no beneficial effects were revealed by the addition of other compounds, including coenzyme Q10, polyvinylpyrrolidone, glucose and glycine. The improvement of post-thaw sperm quality by TEMPOL treatment may be attributed to its ability to scavenge oxygen free radicals and destroying superoxide anions, resulting in intracellular and extracellular protection. This was supported by the trends of parameters assessed in this study: a significant reduction in ROS production and lipid peroxidation, significant increases in sperm motility, integrities of plasma membrane, acrosome and DNA, mitochondrial membrane potential, activities of catalase, superoxide dismutase and succinate dehydrogenase, and glutathione levels. In conclusion, the cell-permeable antioxidant TEMPOL could further improve the published sperm cryopreservation technique in Zhikong scallops.