RESUMO
Various cellular systems have been analysed for synergistic interactions of the simultaneous action of hyperthermia with physical agents including ionizing radiation, ultraviolet light, and ultrasound, and with chemical agents including thio-TEPA and cis-DDP. Some general rules of synergistic interaction were revealed. First, for every constant rate or intensity of exposure to physical factors or concentration of chemical agents, synergy can be observed only within a certain temperature range that is different for various cellular systems. Secondly, within this range, there is a specific temperature that maximizes the synergistic effect. Any deviation of temperature from the optimal one results in a reduction in synergy. Thirdly, the rate of exposure to physical agents or the concentration of chemical agents strongly influences the synergy; i.e. as the dose rate or concentration is reduced, the temperature for maximum synergism decreases. Possible interpretations of the mechanisms responsible for these relationships of synergy are discussed.
Assuntos
Hipertermia Induzida , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos da radiação , Saccharomycetales/efeitos dos fármacos , Saccharomycetales/efeitos da radiação , Antineoplásicos/farmacologia , Antineoplásicos Alquilantes/farmacologia , Cisplatino/farmacologia , Sinergismo Farmacológico , Temperatura Alta , Radiação Ionizante , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomycetales/crescimento & desenvolvimento , Tiotepa/farmacologia , Ultrassonografia de Intervenção , Raios UltravioletaRESUMO
The inactivation of diploid yeast cells of Saccharomyces cerevisiae was studied after simultaneous treatment of ultrasound and hyperthermia. The existence of a definite temperature range was proved within which a synergistic interaction was determined. An optimal temperature that maximized the synergy could be identified. A simple mathematical model of synergistic interaction of damages produced by ultrasound and high temperature has been proposed. The model suggests that synergism is expected from the additional lethal damage arising from the interaction of sub-lesions induced by both agents. The model allows quantitative analysis of the combined action of two agents used to be performed, and predicts the greatest value of the synergistic effect and conditions under which it can be achieved.