Effect of cryoprotective media and dilution methods on the preservation of human spermatozoa

Human Sperm Preservation Medium (HSPM) containing 15% glycerol, 0.05 M sucrose and 1% glycine had an equal or better capacity to preserve sperm motility and vitality than egg yolk-citrate medium (ECM) containing 15% glycerol. Insemination of patients with semen frozen in HSPM resulted in a higher pregnancy rate than semen frozen in ECM. Glycerol was superior to dimethyl sulphoxide (DMSO) or ethylene glycol (EG) as a cryoprotectant, although the cryoprotective ability of 7.5% glycerol and 7.5% EG did not differ significantly. Neither the addition temperature nor the method of addition of the media containing glycerol, DMSO or EG had any influence on the sperm cryosurvival. Raffinose (0.025 to 0.05 M) or sucrose (0.05 to 0.1 M) improved cryosurvival of spermatozoa. The pH of HSPM had no significant influence on the cryosurvival of spermatozoa but the optimal pH was 6.5 to 7. Ratios of 1:1, 1:2, 1:3, and 1:4 of diluent to semen did not affect sperm cryosurvival.