Indicators of oxidative stress after ionizing and/or non-ionizing radiation: superoxid dismutase and malondialdehyde.

Several authors have suggested that low level laser light may have a positive influence on side effects caused by ionizing radiation therapy. We therefore studied indicators of oxidative stress after exposure to gamma radiation with or without pre-exposure to low level laser light. Groups of mice were exposed to light from a laser diode at a wavelength of 830 nm, delivering an energy of 20 or 100 J to 1cm(2) in the abdominal part of the animal with a power density of 300 mW/cm(2) in continuous regime. Following this treatment (or sham irradiation), mice were irradiated with graded doses of (60)Co gamma rays. Levels of superoxide dismutase and malondialdehyde were measured in murine blood cells 30 min or 3 days after exposure. For both time points, there was a clear increase of superoxide dismutase and malondialdehyde with gamma dose, but laser light (alone or in combination with gamma irradiation) did not seem to have any influence on either parameter. Because the physical parameters in our experiments were similar to those of studies showing a positive effect of laser pre-exposure, we conclude that the lack of an observed effect in our case was due to differences in biological parameters, i.e. to differences between the tissues or cell types studied. It is also possible, of course, that laser effects would be seen mainly in the skin immediately exposed, and not to the same degree in blood cells circulating through that area, which were exposed to considerably smaller laser energies.