The Effect of Bone Marrow Injection on the Incorporation of Formate-Carbon-14 into Deoxyribonucleic Acid Purines in X-Irradiated Rats

Abstract

The establishment of the protective effect of intraperitoneal implants of spleen (1), of intraperitoneal or intravenous injection of spleen homogenates (2, 3), and of the administration of bone marrow suspensions (4-6) on otherwise lethally X-irradiated animals has stimulated interest in the mechanisms by which these preparations modify the lethal effect of X-radiation. Among early indications of radiation damage is the inhibition of incorporation of labeled precursor substances into tissue deoxyribonucleic acids (DNA) in Xirradiated laboratory animals. This effect was first demonstrated by Hevesy et al. (7, 8) with inorganic P32 and acetate-C14. An X-radiation dose of 800 r decreases also the incorporation of glycine-C14 into DNA and ribonucleic acid purines of rabbit bone marrow and of rat intestine (9). Previous studies in this laboratory have shown that protection against radiation death in mice (LD,oo dose) afforded by isologous spleen homogenate injection is accompanied by a reversal of radiationinduced inhibition of incorporation of C'4-formate into spleen and bone marrow nucleic acid purines (10) and by a recovery in the spleen DNA levels (11). The present experiments were designed to determine whether modification of radiation injury in rats by rat bone marrow (6) is similarly reflected in changes in nucleic acid metabolism in radiosensitive tissues. Specifically, the effect of injection of rat bone marrow on the incorporation of formate-C14 into DNA adenine and guanine has been studied in selected tissues of lethally X-irradiated rats.