Human spermatozoal tail hypo-osmotic swelling test, motility characteristics in hypotonic saline, and survival of spermatozoa after cryopreservation.

Normozoospermic semen samples (n = 82) were examined to investigate whether the degree of sperm tail swelling in hypo-osmotic medium (fructose and sodium citrate; 150 mOsm/l), and motility characteristics after a 15-min exposure to hypotonic saline (sodium chloride; 150 mOsm/l) could predict the cryosurvival rate (% post-thaw motility/% pre-freeze motility x 100%) of spermatozoa after cryopreservation by the liquid nitrogen vapour freezing method using the TEST-glycerol-egg yolk buffer. The CellSoft automated semen analyser was used to analyse sperm motility in pre-freeze and post-thaw semen samples, and after exposure to hypotonic saline. Sperm tail hypo-osmotic swelling and sperm motility in pre-freeze semen showed no significant correlations (P > 0.05) with the cryosurvival rate. There were significant correlations (P < 0.05) between the cryosurvival rate and the following sperm motility parameters in hypotonic saline: % motility (r = 0.2846), motility index (% motility x curvilinear velocity; r = 0.2809) and % decrease in motility index from the baseline value in semen (r = 0.3378). The % decrease in motility index after hypotonic saline treatment was significantly less (P < 0.05) in the normal (> or = 50% cryosurvival rate; mean +/- SEM 5.9 +/- 3.2%; n = 33) compared with the subnormal (< 50% cryosurvival rate; 27.3 +/- 4.8%; n = 49) cryosurvival groups. This parameter was also determined, by multivariate discriminant analysis, to be capable of classifying each pre-freeze semen sample into either cryosurvival group with 69.5% accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)