Effect of spleen radiation protection factor on nucleic acid metabolism: Reversal of x-radiation-induced inhibition of formate-C 14 incorporation into mouse nucleic acid purines

Abstract

1. 1. The effect of lethal whole-body x-irradiation (750 r.) on the incorporation of formate-C 14 into tissue nucleic acid purines of LAf 1 mice was investigated. In bone marrow and in spleen this incorporation was markedly depressed by the 5th hr. following irradiation. The incorporation approached zero by the 2nd postirradiation day and remained so until the death of the animals. Except for a moderate suppression of incorporation into intestinal DNA-adenine, there was a relatively small effect in intestinal tissue. 2. 2. Postirradiation treatment of the mice by means of a single intraperitoneal injection of spleen homogenate (an agent known to afford protection against radiation death at this dose level) elicited a reversal of the depression of formate incorporation as compared with nontreated mice. Earliest indication of reversal of inhibition appeared on the 5th posttreatment day, in the bone marrow and spleen DNA-adenine fractions. The factor or factors in spleen homogenate responsible for these effects are heat-labile.