LIGHT IRRADIATION OF MOUSE SPERMATOZOA - STIMULATION OF IN-VITRO FERTILIZATION AND CALCIUM SIGNALS

Irradiation of mouse spermatozoa by 630 nm He-Ne laser was found to en hance the intracellular calcium levels and fertilizing potential of th ese cells. The effect of light on calcium transport and on fertilizati on rate was abrogated in the absence of Ca2+ during the irradiation ti me, indicating that the effect of light is Ca2+ dependent. The stimula tory effect of fight on C2+ uptake was abolished in the presence of a voltage-dependent Ca2+-channel inhibitor nifedipine, indicating the in volvement of a plasma membrane voltage-dependent Ca2+ channel. Further more, the stimulatory effect of light was completely inhibited by the mitochondrial uncoupler FCCP, indicating that laser irradiation might affect the mitochondrial Ca2+ transport mechanisms. A causal associati on between laser irradiation, reactive oxygen species (ROS) generation and sperm function was indicated by studies with ROS scavengers, supe roxide dismutase (SOD) and catalase, and exogenous hydrogen peroxide, The SOD treatment, which enhanced H2O2 production, resulted in increas ed Ca2+ uptake and enhanced fertilization rate. On the other hand, cat alase, which decomposes H2O2, impaired the light-induced stimulation i n Ca2+ uptake and the fertilization rate. Taken together, the data sug gest that H2O2 might be involved in the irradiation effects, and indee d laser Irradiation enhances the production of H2O2 by spermatozoa. Th ese results indicate that the effect of 630 mn He-Ne laser irradiation is mediated through the generation of H2O2 by the spermatozoa and tha t this effect plays a significant role in the augmentation of the sper m cells' capability to fertilize metaphase H-arrested eggs in vitro.