Lipid Peroxidation during the Cryopreservation Process of Porcine Spermatozoa
The potential advantages of sperm cryopreservation have not been fully accomplished due to the limiting detrimental effects the freezing process has on sperm structure and composition. Previous studies have suggested that cells suffer lipid peroxidation damage during the cryopreservation process, specifically indicating the damage results from mechanical stress during the preparatory and freezing processes. In this present study, sperm samples were analyzed for lipid stability throughout sample processing through evaluations for lipid peroxidation and lipid free radical concentration. Our analysis was completed in three experiments. In Exp. #1, lipid stability levels were evaluated from five separate boar ejaculates frozen using three different freezing methods to compare cryopreservation techniques. In Exp. #2, lipid peroxidation amounts for fresh post-ejaculate and albumin extended boar samples were compared. Experiment #3 involved evaluations of the semen processing to examine sample and seminal fluid alterations. Samples tested from the freezing protocol included fresh, extended, addition of a wash buffer, cooling to 17 ºC, centrifugation, addition of two egg-yolk extenders, cooling to 5 ºC and postthaw values. Though there was no difference between the three freezing treatments, significant differences were noted between the fresh and extended samples (P < 0.001). These findings were exemplified by the step by step analysis of the processing and freezing protocol. The lipid peroxidation amounts accumulated after each the procedural step (P < 0.001). Significant differences were also observed in the lipid radical levels (P < 0.001). The results of the pre-freezing protocol, alterations in lipid stability do not appear to be due to thermal or mechanical stress. The largest gains of both lipid parameters developed after the addition of an egg-yolk freezing extender. The results suggest further studies in alterative extenders are needed.
