Influence of media and thermal shock on sperm capacitation

To elucidate the influence of medium and thermal shock in inducing sperm capacitation, eight ejaculates were processed as follows. Each ejaculate was divided into three aliquots. To two of the aliquots, an equal volume of saline was added, while TEST-yolk was added to the remaining aliquot. All three samples were cooled slowly to 5 degrees C and incubated for 18-20 h. After aspirating the supernatant, 6 ml of Tyrode solution containing 0.06 g% egg yolk, warmed to 37 degrees C was added without disturbing the sperm pellet to the aliquot containing TEST-yolk and to one of the aliquots mixed with saline. To the remaining saline-processed sperm pellet, 6 ml TEST-yolk (37 degrees C) was added. All samples were washed twice (400 x g for 5 min) and processed for the sperm penetration assay (SPA). Samples, either pre-incubated in TEST-yolk (mean +/- SEM; 65.9 +/- 11.7%) or warmed (thermal shock) with TEST-yolk (62.6 +/-12.1%) yielded significantly (P < 0.05) higher SPA outcome than the samples processed and warmed with saline (17.8 +/- 12.0%). The penetration indices were not statistically different from each other. It therefore appears that the medium influences the sperm capacitation process to a greater extent and may augment the influence of thermal shock.