Cytocidal effect of rifamycin derivatives on ascites tumor cells: studies with [125I]iododeoxyuridine.

The cytotoxicity of 2 rifamycin derivatives, rifazone-82 and rifampicin, on mouse ascites cells was studied, using the [125I]iododeoxyuridine (IUDR) method of labeling the tumor cells. This technique allows a distinction to be made between a cytocidal and cytostatic effect. The 2 drugs exerted a cytocidal effect against 2 non-leukemic cell lines, but had no effect against 3 leukemic lines.