Patterns of Synergic Interaction Display after Heavy Metals Combined with Hyperthermia or Ionizing Radiation

—The objective of this study was to identify the general patterns of synergism display after the simultaneous action of heavy metal salts with ionizing radiation or with hyperthermia. The objects of research were Escherichia coli bacteria (strain B/r ) and diploid yeast cells of Saccharomyces cerevisiae (strain XS800), which were treated with chemical preparations containing salts of heavy metals (copper, platinum, lead, chromium, zinc) at the stationary stage of growth simultaneously with hyperthermia (37–60°С) or ionizing radiation (γ‑rays 60 Co, dose rate 10.8 Gy/min). To demonstrate the generality of the patterns revealed, we used data on the inactivation of Chinese hamster cells (CHO) published by other authors. To quantify the degree of synergism, we used a synergistic enhancement ratio determined by the division of isoeffective doses on the theoretically predicted and experimental dose-response curves. The experimental results on cell survival and the synergistic interaction of the simultaneous application of heavy metal salts with ionizing radiation or hyperthermia are presented. The optimal parameters of acting agents that provide the highest synergistic interaction have been revealed. Any deviation of these parameters from the optimal value leads to a decrease in synergism. It is concluded that there exists a general pattern that does not depend on the nature of the acting agents, biological objects, and tests. Possible mechanisms of the results and directions of their practical application in radiobiology and ecology are discussed.