Changes in radiosensitivity induced by cyclic nucleotides and chemical radioprotection.

Cyclic AMP has a radioprotective effect and its aministration results in a significant increase in LD50/30 values in Chinese hamsters. The efficiency of these radioprotective effects is comparable to that of such radioprotective compounds as AET and cystamine + mexamine. Cyclic GMP is responsible for significant radiosensitizing effects. Changes in radiosensitivity after administration of cyclic nucleotides are both immediate and delayed and correlate closely with dose and time of administration.