Evaluation of sperm cryoprotective media in respect to fertilizing capacity tested in vitro

Nine different cryoprotectant buffers were tested to measure their protective ability towards main sperm seminological parameters. These were: maintained sperm motility, progressive motility and sperm viability. Out of the nine tested buffers, medium E (TES-Tris without glycerol) and H (glycerol only) showed significantly lower (P < 0.001) values than the rest of the studied buffers in respect to all tested seminological features. The other media did not differ significantly in their cryoprotective abilities to sperm. Richardson's medium (A) preserved sperm viability significantly better (P < 0.001) than the other tested buffers, reaching 63.1% of viable spermatozoa in proportion to the fresh sperm sample before freezing. Three cryoprotectants, A (with egg yolk, no TEST buffer system), D (neither egg yolk nor TEST buffer system), F (TEST-egg yolk buffer system) were further studied for their ability to preserve sperm function in sperm-cervical mucus penetration (Penetrak) and sperm penetration assay (SPA). In our hands, neither supplementation of the buffer with egg yolk nor TEST-egg yolk buffer system promoted sperm capacity in functional tests. A,D,F buffers did not significantly differ among each other in applied functional assays, however, they all diminished (P < 0.001) sperm penetration ratios when compared with fresh sperm samples. Therefore enhancement of sperm capacity to fertilize after equilibration with TEST-egg yolk buffer system should be contested.