Laser irradiation of mouse spermatozoa enhances in-vitro fertilization and Ca²⁺ uptake via reactive oxygen species

630 nm He-Ne laser irradiation was found to have a profound influence on Ca²⁺ uptake in mouse spermatozoa and the fertilizing potential of these cells. Laser irradiation affected mainly the mitochondrial Ca²⁺ transport mechanisms. Furthermore, the effect of light was found to be Ca ²⁺-dependent. We demonstrate that reactive oxygen species (ROS) are involved in the cascade of biochemical events evoked by laser irradiation. A causal association between laser irradiation, ROS generation, and sperm function was indicated by studies with ROS scavengers, superoxide dismutase (SOD) and catalase, and exogenous hydrogen peroxide. SOD treatment resulted in increased Ca²⁺ uptake and in enhanced fertilization rate. Catalase treatment impaired the light-induced stimulation in Ca²⁺ uptake and fertilization rate. Exogenous hydrogen peroxide was found to enhance Ca ²⁺ uptake in mouse spermatozoa and the fertilizing capability of these cells in a dose-dependent manner. These results suggest that the effect of 630 nm He-Ne laser irradiation is mediated through the generation of hydrogen peroxide by the spermatozoa and that this effect plays a significant role in the augmentation of the sperm cells' capability to fertilize metaphase II-arrested eggs in-vitro.