Interaction between prostasomes and spermatozoa from human semen

Prostasomes are prostate-derived organelles that occur freely in human seminal plasma. They promote forward motility of spermatozoa probably by closely interacting with them in an unknown manner. We have studied the interaction between human prostasomes and spermatozoa by applying them as two separate samples in free-zone electrophoresis. During the run these samples approached each other and finally fused into one single peak that was not further dissociated. Both the spermatozoa and prostasomes displayed a net-negative surface charge, the latter being less negative. This discrepancy in charge was even more pronounced by pretreatment of prostasomes with neuraminidase, which, however, did not affect the interaction. This implies a strong interaction of a probable hydrophobic character between cells and organelles. The presence of prostasomes and spermatozoa in the fused, single peak was confirmed by transmission electron microscopy. Evidence for interaction was apparent in transmission electron microscopy after embedding in a hydrophilic, but not in a hydrophobic, resin. This observation supports the view that the bonds between prostasomes and spermatozoa are of hydrophobic character. This type of interaction enables the prostasomes to act in close vicinity to spermatozoa and may create the prerequisites for a proper microenvironment of the spermatozoa favoring their forward motility.