Changes in calcium transport in mammalian sperm mitochondria and plasma membranes caused by 780 nm irradiation

Background and Objective: Regulation of intracellular Ca²⁺ concentrations are very important in control of sperm motility and acrosome reaction. It was shown previously that low-power lasers in the visible and near-infrared range alter Ca²⁺ uptake by sperm cells. In the present work the effect of a 780 nm diode laser on Ca²⁺ uptake by sperm mitochondria and isolated plasma membrane vesicles is investigated. Study Design/Materials and Methods: Digitonin-treated spermatozoa and plasma membrane vesicles were irradiated with a 780-nm diode laser at various powers and energy doses, and Ca²⁺ uptake was measured by the filtration method. Results: It was found that 780-nm irradiation inhibits Ca²⁺ up-take by the mitochondria but stimulates Ca²⁺ binding by sperm plasma membrane vesicles. The effect of light on Ca²⁺ uptake by plasma membrane vesicles in the absence of ATP was much larger than that measured in the presence of ATP. Addition of Ca²⁺ ionophore decreased the Ca²⁺ uptake by the irradiated membranes in the presence of ATP but enhanced it significantly in the absence of ATP. Conclusion: 780 nm light inhibits Ca²⁺ uptake by sperm mitochondria and enhances Ca²⁺ binding to sperm plasma membranes.