THE INCORPORATION OF C14-LABELLED FORMATE INTO THE TISSUE NUCLEIC ACIDS OF RATS BEARING THE NOVIKOFF HEPATOMA

Abstract

A study was made of the incorporation in vivo of C14-labelled formate into purines and pyrimidines of the nucleic acids of various tissues of normal rats and rats bearing the Novikoff hepatoma. The purines of the intestinal mucosa and the hepatoma had the highest specific activities, followed in descending order by those of spleen, kidney, testes, and liver. The pyrimidines of the mucosa and hepatoma also exhibited comparatively high specific activities. It was felt that the incorporation of radioactivity by a given tissue was related to its rate of cell renewal and that the present findings did not indicate a difference between tumor and normal tissue with respect to mechanisms involved in the biosynthesis of the nucleic acids. The results indicated that the tissue nucleic acids of the tumor-bearing animals incorporated more radioactivity than did those of normal rats. Chemical degradation of the radioactive purines showed that part of the radioactivity was derived from the injected C14-formate and part from C14O2 formed by metabolic oxidation of the formate.