Dibutryl cyclic adenosine monophosphate: effect on radiosensitivity of tumors and normal tissues in mice.

The effect of dibutryl cyclic adenosine monophosphate (db-cAMP, 30 mg/kg), injected into mice before irradiation, on the radiation sensitivity of various tissues was investigated. Survival of proliferating hair follicles, small gut stem cells, fibrosarcoma (FSa) micrometastases in the lungs, and two different mammary carcinomas, as assayed by the TCD50 method, were studied. Intraperitoneal injection of db-cAMP before irradiation resulted in higher survival of hair follicles irradiated on the third day after plucking. Stem cells in the small gut showed increased survival if irradiated 4 hours after injection. There was no effect on the survival of FSa micrometastases by preinjection and the TCD50/120 days of the mammary carcinomas was not altered.