Chemical modification of 5-[125I]iodo-2'-deoxyuridine toxicity in mammalian cells in vitro.
OBJECTIVE
To address the cytotoxic effects of DNA-incorporated (125)I in Chinese hamster V79 lung fibroblasts under various scavenging conditions.


METHODS
The toxic effects of DNA-incorporated 5-[(125)I]iodo-2'-deoxyuridine ((125)IdUrd) were assessed by the colony-forming assay with cells incubated in medium containing serum and/or dimethyl sulphoxide (DMSO). Experiments were carried out at 0.3 or -135 degrees C.


RESULTS
When (125)I decays were accumulated at 0.3 degrees C in 10% serum 0, 5 or 10% DMSO, no radioprotection was afforded by 5% DMSO, while the dose modification factor (DMF) for 10% DMSO was 2.0. For cells accumulating decays at 135 degrees C in the presence of 5 or 10% serum, DMSO was radioprotective (DMF= 1.8-1.9). D(0) obtained at each serum concentration correlated strongly (R=0.999) with the scavenging capacity of DMSO. Under these experimental conditions, 10% serum is approximately 3.6 times more protective than 5% serum.


CONCLUSIONS
The contribution of indirect mechanisms to the toxicity of (125)I decaying within mammalian cell nuclear DNA can be demonstrated not only with DMSO, but also with the hydroxy radical scavengers present in serum.
Walicka
M A
MA
Department of Radiology, Harvard Medical School, Boston, MA 02115, USA.
Adelstein
S J
SJ
Kassis
A I
AI
D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003080:Cold Temperature; D006224:Cricetinae; D003412:Cricetulus; D003451:Cryoprotective Agents / Q000494:pharmacology; D003470:Culture Media; D004247:DNA / Q000378:metabolism / Q000633:toxicity*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D005615:Freezing; D007065:Idoxuridine / Q000378:metabolism / Q000633:toxicity*; D007457:Iodine Radioisotopes / Q000633:toxicity*; D019275:Radiopharmaceuticals / Q000378:metabolism / Q000633:toxicity*
D003451:Cryoprotective Agents; D003470:Culture Media; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D004247:DNA; D007065:Idoxuridine; D004121:Dimethyl Sulfoxide