Protective effect of chemical radiosensitizers on proand eukaryotic cells under the action of ultraviolet light

The use of chemical radiosensitizers to increase the effectiveness of radiation therapy and simultaneous reduction of radiation exposure to a patient is known and widely used in cancer therapy. The development of existing and the search for new principles for the use of radiomodifiers is still relevant. The use of the hypothesis of the representation of ionizing radiation by the combined action of ionization and excitation processes of molecules and atoms of the irradiated substance, the ability of some well-known chemical radiosensitizers to exhibit their properties only under the excitation modeled by ultraviolet radiation (254 nm) is investigated. The following radiosensitizers were used as chemicals: metronidazole, methatrexate, endotaxan, carboplatin, fluorouracil and cisplatin. The aim of the study is to determine the characteristics of the action of chemicals known as ionizing radiation sensitizers in relation to ultraviolet light. Bacterial and yeast cells (pro- and eukaryotes) served as an object of influence. All these chemicals turned out to be protectors to the action of ultraviolet light, protecting cells from UV radiation. Thus, the dose modifying factor for metronidazole was more than 45, methotrexate was more than 70, and for other drugs - from 2 to 5. The exception was the drug cisplatin, with the dose modifying factor is 1. The protective effect depends on the irradiation conditions: an aqueous suspension or a cells monolayer. Based on the hypothesis of representing ionizing radiation as a joint action of two physical factors differing in biological effect, it can be assumed that the interaction of sub-damages caused separately by ionization and excitation of molecules and atoms can be additive, synergistic or antagonistic. It follows from this that the nature of modification of excitation processes by chemicals can significantly affect the effectiveness of sensitization by ionizing radiation. To achieve maximum effect, it is necessary to use chemicals that sensitively affect both the excitation processes under the action of ionizing radiation and ionization. It is the approach to the search for new chemical radiosensitizers that will increase the efficiency of ionizing radiation modification.