Nuclear phenotype evaluation in skeletal muscle from Wistar rats exposed to low-level lasers

Low-level laser therapy includes devices emitting red and near-infrared radiation with output power below 100 mW. These devices are successfully used for the treatment of injuries and to improve exercise performance based on their biomodulatory effect. Despite the wide use of clinical protocols based on these lasers, the laser-induced effects on DNA are still disputed. Thus, the objective of this study was to investigate chromatin organization, ploidy degrees, and DNA fragmentation in skeletal muscle tissue from Wistar rats exposed to low-level red and infrared lasers. Wistar rats were exposed to low-level red and infrared lasers (25, 50, and 100 J cm(-2), 100 mW, continuous-wave emission mode) and, after 24h, samples of this tissue were withdrawn for the analysis of chromatin organization, ploidy degrees, and DNA fragmentation by Feulgen reaction detection of micronucleus, and apoptosis by TUNEL assay. Data obtained show that low-level red and infrared lasers alter geometric and densitometric parameters as well ploidy degree in muscle nuclei from Wistar rats, but do not induce DNA fragmentation, chromatin loss, and apoptosis at fluences taken out from clinical protocols.