Effect of purine nucleosides and nucleotides on the in vivo radiation response of normal tissue in the rat

WAG/Rij rats were exposed to single doses of radiation following intraperitoneal injection of inosine, pyruvate and inorganic phosphate (IPP). When skin reactions and structural damage were scored in the hind legs of irradiated rats, IPP was observed to decrease radiation sensitivity. Radioprotection was also observed in rats that were pretreated, with inosine alone and with the purine nucleosides adenosine and guanossine. The purine nucleotides 5′-inosine monophosphate (IMP), 5′-adenosine monophosphate (AMP), 5′-guanosine monophosphate (GMP) and cyclic adenosine 3′,5′-monophosphate (cyclic AMP) were also protective. The purine bases hypoxanthine, adenine and guanine were not protective. A decline in blood pressure was observed following administration of either IPP or inosine alone but not following AMP or cyclic AMP. The mechanism(s) whereby the purine nucleosides and nucleotides result in radioprotection are currently being investigated.