Effect of seminal plasma on functional integrity of rabbit sperm membranes during storage at 4ºC or freezing.

Abstract

The effect of semen plasma removal either by simple centrifugation or by separation through a Percoll gradient on the integrity of plasma membranes of rabbit spermatozoa during storage at 4ºC and freezing was evaluated in two successive experiments. A modifi ed hypo-osmotic swelling test procedure combined with supravital staining was employed to evaluate simultaneously membrane integrity of head and tail membranes of sperm cells. In the fi rst experiment, the impact of semen plasma on membrane integrity of sperm cells was examined in Tris-citric acid-glucose extender at 4ºC for 96 h. The percentage of sperm cells with disintegrated tail and head membranes increased in all groups in correlation with the length of storage. After storage for 96 h, removal of semen plasma, irrespective of the method of removal, resulted in signifi cant increase (P<0.01) in the percentage of sperm cells with disintegrated plasma membranes. The adverse effect of storage and removal of semen plasma was more prominent on the tail membranes, and especially during the fi rst 24 h of the storage period. In the second experiment, the impact of semen plasma on membrane integrity of sperm cells undergoing freezing was examined. A total of three groups were arranged as described in the fi rst experiment, and semen samples were frozen in straws using an extender including acetamide and methyl cellulose. Freezing of semen drastically reduced the percentage of sperm cells with intact plasma membranes in postthaw samples. However, removal of semen plasma, irrespective of the method of removal, did not affect the proportion of sperm cells with intact plasma membranes. In conclusion, the effect of semen plasma on plasma membranes varied signifi cantly relative to the preservation temperature of sperm cells. Although it exerted a protective infl uence during storage at 4ºC, no protective impact was monitored during freezing.