Radioprotection by Dmso Against the Biological Effects of Incorporated Radionuclides in Vivo: Comparison with other radioprotectors and evidence for indirect action of Auger electrons

Abstract

Dimethyl sulfoxide (DMSO) was studied for its capacity to protect against the biological effects of chronic irradiation by incorporated radionuclides. Spermatogenesis in mice was used as experimental model and spermatogonia! cell survival was the biological endpoint. DMSO was injected intratesticu-larly 4 h prior to a similar injection of the radiochemical and the spermhead survival determined. Iodine-125 was localized in either the cytoplasm (H¹²⁵IPDM) or in the DNA (¹²⁵IUdR) of the testicular cells. Protection was observed against the high-LET type effects of DNA-bound ¹²⁵I as well as the low-LET effects of cytoplasmically localized ¹²⁵I with dose modification factors (DMF) of 3.1 ± 1.0 and 4.4 ± 1.0 respectively. No protection (DMF = 1.1 ± 0.1) was observed against the effects of high-LET 5.3 MeV alpha particles of ²¹⁰Po. The present findings provide supporting evidence that the mechanism responsible for the extreme biological damage caused by DNA-bound Auger emitters is largely radical mediated and therefore indirect in nature.