EFFECT OF CENTRIFUGE SPEED, REFRIGERATION MEDIUM, AND SPERM WASHING MEDIUM ON CRYOPRESERVED SPERM QUALITY AFTER THAWING

Cryopreservation and subsequent thawing of semen for assisted reproduc tive procedures decreases sperm motility; motility further reduces whe n the cryoprotectant medium is removed because of the osmotic shock an d centrifugation done to prepare the sperm. To compare motility and th us pregnancy rates, this study examined the effects of adding an addit ional refrigeration medium and three different centrifugation speeds f or sperm preparation. Semen samples from 16 healthy normal volunteers were obtained by masturbation after 48 h of abstinence. Sperm motility and other motion characteristics were analyzed with a computer-assist ed semen analyzer before freezing, after thawing, and after centrifuga tion. Each sample was divided into 6 aliquots and frozen using the liq uid nitrogen vapor method. After thawing, human tubal fluid (HTF) with 5% human serum albumin was added to 3 aliquots, and refrigeration med ium (identical to freezing medium without glycerol) was added to the r emaining 3 tubes for each specimen. The tubes containing the two media were then washed by centrifugation at 100g, 300g, and 500g for 10 min . Aliquots with refrigeration medium did not significantly differ from those with HTF for percent motility, curvilinear velocity, straight-l ine velocity, and amplitude of lateral head displacement at any centri fugation speed. Motile sperm count was significantly greater only at 1 00g and 300g for refrigeration medium (p = .02 and .01) and HTF (p = 0 .001); at 300g, average path velocity in refrigeration medium aliquots (p = .01) and linearity in HTF (p = .01) were greater. The results in dicated that the reduction in motility and other motion characteristic s probably cannot be overcome by changing factors such as the sperm pr eparation medium or centrifugation speed. More effective cryopreservat ion techniques or preparation methods that eliminate centrifugation ne ed to be developed.