In vitro effects of cationic compounds on functional human sperm parameters.

To determine the mechanisms of spermicidal activity by cationic compounds. In vitro study with human sperm. Academic research institute in collaboration with a university hospital. Normozoospermic men providing samples for routine analysis or assisted reproductive technologies. In vitro incubation of sperm with commercially available cationic surfactants. The effects of benzalkonium bromide (C12Bzk), pyridinium bromide (C12Pyr), and dodecyl trimethylammonium bromide (C12TAB) on human sperm viability, motility, mitochondrial status, capacitation, acrosomal status, and calcium movements were monitored. There was a universal decrease in mitochondrial membrane potential after 180 minutes. Incubation with C12Bzk led to less capacitated sperm at LD50 after 180 minutes (46.0%) as well as to 20.2% of cells significantly increasing their intracellular calcium. C12Pyr was the stronger compound, affecting capacitation and acrosomal status at LD50 and promoting a higher calcium influx (81.7%). C12TAB increased the number of acrosome-reacted sperm at LD50 after 180 minutes and led to a significant increase in calcium signaling (61.2% and 67.9%, respectively). Cationic surfactants seem to impair sperm function at various levels, although C12Pyr was shown to be more effective. Given the concentrations used, these compounds are not necessarily acting as surfactants. To our knowledge, this is the first study that evaluates contraceptive compounds by monitoring sperm calcium signaling, and this seems to be a sensitive parameter in terms of determining the action of putative spermicides.