Lesions in DNA of hypoxic mammalian cells irradiated in the presence of TAN.

TAN (triacetoneamine-N-oxyl) at a concentration of 10 mM gives a dose modifying factor (DMF) of 1.45 for the surviving fraction of gamma-irradiated hypoxic mammalian cells. Under the same conditions, however, TAN produces little or no enhancement of single strand breaks (SSB) in DNA (DMF congruent to 1). In this study, enhancement of the type of DNA lesions exposed by an extract of M. luteus is reported. The DMF for this type of damage (MLS) is 1.5. TAN is known to affect the size of DNA synthesized after irradiation, presumably by causing interruptions in synthesis at TAN-DNA adduct sites. The absolute number of M. luteus extract sensitive sites detected in this work corresponds to approximately on half of the number of sites of interrupted synthesis. In its sensitizing effect on DNA, the free radical TAN is different from the electron affinic drug, misonidazole.