VITAMINS AS RADIOPROTECTORS IN-VIVO .1. PROTECTION BY VITAMIN-C AGAINST INTERNAL RADIONUCLIDES IN MOUSE TESTES - IMPLICATIONS TO THE MECHANISM OF DAMAGE CAUSED BY THE AUGER EFFECT

The potential of vitamin C, an antioxidant, to protect the radiosensit ive spermatogonial cells in mouse testes against the effects of chroni c irradiation by radionuclides incorporated into tissue was investigat ed. Interestingly, when injected intratesticularly, a small and nontox ic amount of vitamin C (1.5 mu g in 3 mu l saline) protected the sperm atogonia against the damage associated with high-LET radiation caused by Auger electrons from similarly administered 5-(I-125)-iodo-2'-deoxy uridine ((125)IdU). A dose modification factor (DMF) of 2.3 was obtain ed. In contrast, no protection was observed when Po-210, an alpha-part icle emitter, was administered similarly. These findings suggest that the mechanism of action of the Auger effect is of an indirect nature, which is in contrast to the direct action generally believed to be res ponsible for biological damage caused by high-LET radiations.