AIMThe study was designed to examine the effects of cryoprotective media, and glycerolating and thawing procedures on human sperm motility and gel penetrating ability.

METHODFifteen unselected donors provided semen varying in quality that was distributed in a factorial design across three cryoprotectants (glycerol, egg yolk-citrate-glucose-glycerol and egg yolk-tris-glucose-glycerol). Also, glycerol was added at room temperature versus at 4 degrees C. Two thaw temperatures were tested (laboratory air temperature for 10 min versus a 65 degrees C waterbath for 4 seconds). The proportion of total and progressively motile sperm was estimated immediately after thawing and following incubation at 35 degrees C for 2 h. Migration of sperm for 30 min at 37 degrees C through polyacrylamide gel was tested.

RESULTSDonors differed greatly, with post-thaw total motility of sperm ranging from 9 to 44% (P<0.05). Egg yolk-citrate-glucose-glycerol and egg yolk-tris-glucose-glycerol were superior to glycerol alone (post-thaw values of 35, 37 and 21%, respectively, P<0.05). This was due primarily to poor sperm survival when semen was cooled to 4 degrees C without glycerol or egg yolk. The two thaw temperatures gave similar results. Sperm migration tests paralleled the motility results, but were more sensitive in detecting differences.

CONCLUSIONEgg yolk, particularly in a tris-based medium that is widely used in domestic animals, improved the cryopreservation of both good and poor quality human semen.