Abstract
Summary
Cysteine greatly reduces the sensitivity of rats and mice to lethal amounts of x-rays delivered at either high or low dose rates provided that the amino acid is given before the exposure. Rather comparable protection is obtained when cysteine is injected intravenously in rats immediately or 1 hour before irradiation with 800 r (90% reduction in the 28-day mortality). Injection immediately after exposure or 6 or 24 hours before is without influence. Cysteine also improves survival significantly when it is given orally 30 to 60 minutes prior to the irradiation. Glutathione (I.V. but not oral) can also diminish radiation toxicity. Cystine, methionine, ascorbic acid, and sodium sulfide do not alter survival of the irradiated animal. Results with colloidal sulfur are equivocal. The possible significance of these observations is discussed.
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