Inhibition of the semiconservative DNA synthesis and potentiation of the unscheduled DNA synthesis by 5-nitroimidazole derivatives with an imidazolium or pyridinium ring.

The effects of four pyridinium and one imidazolium derivatives of 5-nitroimidazole have been tested for their action on the kinetics of DNA semiconservative synthesis and of the unscheduled DNA synthesis carried out by TC-SV40 cells. Unscheduled synthesis was induced by 25 Gy X-rays, and the kinetics were evaluated through the measurement of the newly synthetized DNA labelled with [3H-methyl]thymidine. All derivatives inhibit the DNA semiconservative synthesis and increase the unscheduled DNA synthesis to different degrees, but not in the suitable way to reveal the mechanism of interaction with DNA as responsible of the product's radiosensitizing actions on the same mammalian tumor cells.