Comparative Effect of Low‐intensity Laser Radiation in Green and Red Spectral Regions on Functional Characteristics of Sturgeon Sperm

A comparative study of the effect of low‐intensity laser radiation in green (λ = 532 nm) and red (λ = 632.8 nm) spectral regions at equal average irradiance (3 mW cm−2) on functional characteristics of Siberian sturgeon spermatozoa is carried out. Confirmation of the photobiomodulation effect of the radiation is obtained by analyzing spermatozoa motility, percentage of motile spermatozoa and fertilization rate. It is shown that, depending on the energy dose, the laser radiation in red and green spectral regions can have both stimulatory and inhibitory effects on spermatozoa motility. Contrary to popular belief that the short‐wavelength radiation has great prospects in reproductive biotechnologies (due to more efficient absorption of radiation by cellular chromophores and increased generation of ROS), convincing evidence of a more pronounced stimulatory effect of radiation in the red spectral region was obtained. For the first time, metal‐free porphyrins capable of acting as endogenous photosensitizers generating ROS were detected and identified in animal sperm. Using luminol‐dependent chemiluminescence, it is shown that the increased production of ROS capable of exerting an inhibitory effect on biological systems at high concentrations is among the possible reasons for reduction in the stimulatory effect of radiation when moving from red to green spectral region. Photobiomodulation effects of low‐intensity laser radiation in green (532 nm) and red (632.8 nm) spectral regions on Siberian sturgeon spermatozoa are compared. It is shown that, depending on the energy dose, red and green laser radiation can have both stimulatory and inhibitory effects on functional parameters of spermatozoa. It is convincingly demonstrated that, at equal parameters and optimal energy doses, the laser radiation in the red spectral region has a higher stimulatory effect. For the first time, metal‐free porphyrins capable of acting as endogenous photosensitizers generating ROS were detected and identified in animal sperm. Mechanisms of light‐induced effects are discussed.