Total and specific activities of superoxide dismutase (SOD) in seminal plasma are related with the cryotolerance of jackass spermatozoa

This study investigated whether the activities of four antioxidant enzymes present in jackass seminal plasma (SP), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) and glutathione reductase (GSR), are related to the sperm ability to withstand cryopreservation. Eighteen ejaculates from 16 healthy jackasses were collected and split into two aliquots. The first one was centrifuged (3,000×g, 4 °C for 10 min) and used to determine the activities of these four enzymes in SP, whereas the other was diluted in a skim-milk extender and then cryopreserved. Assessment of sperm motility and membrane integrity was performed before and after cryopreservation. Based on the percentages of total motile and viable spermatozoa at post-thaw, samples were classified as good (GFE) or poor (PFE) freezability ejaculates through cluster analyses. Total and specific activities of SOD in seminal plasma were higher (P < 0.05) in GFE than in PFE, whereas no significant differences between GFE and PFE were observed regarding total and specific activities of CAT, GPX and GSR. However, post-thaw sperm parameters were positively correlated with total and specific activities of CAT and negatively correlated with those of GSR. In conclusion, determination of total and specific activities of SOD in the seminal plasma of a given jackass ejaculate may predict the sperm ability to withstand cryopreservation. In addition, our results warrant further research on addressing whether SOD activity in seminal plasma does not only allow predicting the sperm cryotolerance of a given ejaculate but also that of all ejaculates from a given jackass.