THE COMPARATIVE UPTAKE OF I-125-LABELED 5-IODO-2'-DEOXYURIDINE AND THYMIDINE-H3 INTO TISSUES OF MICE BEARING HEPATOMA-129.

Abstract

Summary The distribution of radioactivity has been compared among the DNA, cold acid-soluble, and protein fractions of the liver, spleen, small intestine, and tumor of female C3H mice bearing subcutaneously implanted Hepatoma-129, following the administration of equivalent amounts of I125-labeled 5-iodo-2′-deoxyuridine (IUdR-I125) and thymidine-H3 (TdR-H3). A striking difference in the metabolic fate of these 2 compounds was indicated by the more rapid decrease of radioactivity of the cold acidsoluble fraction derived from IUdR-I125. A hypothesis in explanation of these results has been presented. In agreement with previous reports, thymidine was utilized preferentially to IUdR for the biosynthesis of DNA. The amount of radioiodide derived from IUdR-I125 that appeared in the protein fraction of spleen, small intestine, and tumor, but not of liver, was a very small percentage of that present in the DNA fraction. The relative merits of thymidine and IUdR as a marker for studies of the biosynthesis of DNA, cell turnover, and other biologic problems are discussed.