IN-SITU DETECTION, BY SPIN-TRAPPING, OF HYDROXYL RADICAL MARKERS PRODUCED FROM IONIZING-RADIATION IN THE TUMOR OF A LIVING MOUSE

Hydroxyl radicals are thought to be responsible for the toxicity assoc iated with ionizing radiation in tissues. Measurements of hydroxyl rad icals generated by ionizing radiation in cellular systems have failed thus far to elucidate higher-level homeostatic responses to this and o ther reactive oxygen species. Careful assessment of prior indirect hyd roxyl radical assays in living tissues indicates that they are prone t o a variety of artifacts, making all but the most qualitative relation ships difficult to establish. This paper describes the detection of hy droxyl radicals produced during radiation in the leg tumor of a living mouse, where the free radicals evolve; detection uses low-frequency e lectron paramagnetic resonance in combination with in vivo spin trappi ng. To our knowledge, this is the first report of such a direct measur ement of free radical production in the tissues of a living animal.