Differential Modification of Oxic and Anoxic Radiation Damage by Chemicals: I. Simulation of the Action of Caffeine by Certain Inorganic Radical Scavengers

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Abstract
Caffeine affords partial radioprotection against oxic damage, but potentiates anoxic damage in dry and presoaked barley seeds. Since earlier studies have implicated a physicochemical pathway of action for such differential modification by caffeine, the effect of inorganic substances, known to scavenge specific categories of free radicals, on the oxic and anoxic components of radiation damage was investigated. It is found that the radiation-induced oxic damage is significantly reduced by potassium permanganate, potassium iodide, potassium nitrate and potassium ferrocyanide which scavenge predominantly .H + eaq-, .OH, eaq- and .OH radicals, respectively. Each of these 4 substances, like caffeine, also potentiates anoxic damage in dry seeds, but the anoxic damage in presoaked seeds is potentiated only by potassium ferrocyanide. These results do not confirm the view in the literature that the anoxic sensitization is largely mediated by .OH radicals. A discussion of these observations and the validity of comparing our seed data with those derived from experimental with bacterial spores and naked DNA solutions is presented.