RESUMEN
The possibility of using the antibiotic bleomycin as a part of a hybrid molecule consisting of a targeting fragment and a generator of reactive oxygen species has been investigated. The bleomycin-iron (II) complex was shown to destroy the plasma membrane of thymocytes by producing reactive oxygen species. Antioxidants protected the cells from destruction thus pointing to its free-radical mechanism. The protective effects of catalase and superoxide dismutase indicate that superoxide radical and hydrogen peroxide being formed during autooxidation of the complex are involved in cell damage. The covalent binding of bleomycin to targeting molecules (concanavalin A, insulin, and calcitonin) enhanced the ability of the bleomycin-iron (II) complex to destroy the plasma membrane of thymocytes.