Antioxidants modify the effect of X rays on blood vessels

It was recently shown, with the chicken embryo chorioallantoic membrane (CAM) model, that X rays decrease the number of blood vessels within the first hours after irradiation. In the present study, the possible role of reactive oxygen species (ROS) and nitric oxide (NO) in this effect of X rays was evaluated.

An area of 1 cm2 of the CAM, restricted by a plastic ring, was irradiated at room temperature, in the presence or absence of the tested agents. The number of vessels was measured 48 h after irradiation of the tissue.

Superoxide dismutase and tempol, which are superoxide ion scavengers and catalase, a hydrogen peroxide scavenger, had additive effects, while dimethylsulfoxide, a hydroxyl radical scavenger, reversed the vascular targeting effect of X rays. The combination of X rays with W1400, a selective inducible NO synthase (NOS) inhibitor, had an additive effect on the decrease in number of CAM blood vessels. In contrast, L-NAME, a non-selective NOS inhibitor and D-NAME, its inactive analog, reversed the vascular-targeting effect of X rays, possibly due to their ability to act as potent hydroxyl radical scavengers.

The above data collectively suggest that hydroxyl radicals mediate the damaging effects of X rays on CAM blood vessels, while antioxidants against other ROS do not protect against the vascular-targeting effect of X rays.