RADIOPROTECTION AGAINST LETHAL DAMAGE CAUSED BY CHRONIC IRRADIATION WITH RADIONUCLIDES IN-VITRO

To examine the capacity of chemical protectors to mitigate damage caus ed by chronic irradiation by incorporated radionuclides in vitro, cell s must be maintained in the presence of the protector during the cours e of the irradiation. Such long exposures to chemical protectors at co ncentrations high enough to afford protection usually results in extre me chemotoxicity. To overcome this problem, experimental conditions we re developed to allow Chinese hamster V79 cells to be maintained in 5% DMSO for prolonged periods (up to 72 h) with no observable chemotoxic ity. Under these conditions, the capacity of DMSO to protect against d amage to V79 cells caused by unbound P-32 and (H2O)-H-3 and DNA-incorp orated (131)IdU, [H-3]dThd and (125)IdU was examined. The dose modific ation factors for (32)p, (H2O)-H-3, (131)IdU, [H-3]dThd and (125)IdU w ere 2.6 +/- 0.5, 2.3 +/- 0.3, 1.0 +/- 0.1, 1.16 +/- 0.07 and 1.07 +/- 0.02, respectively. These results show that 5% DMSO is capable of prot ecting cultured V79 cells against lethal damage caused by beta particl es emitted by unbound P-32 and (H2O)-H-3, whereas little or no protect ion is afforded against damage caused by beta particles emitted by DNA -incorporated I-131 and H-3 or low-energy Auger electrons emitted by D NA-incorporated I-125. (C) 1998 bg Radiation Research Society.