Specific activities of the UTP pools of human lymphocytes after uridine- 3 H labeling.

Human lymphocytes were labeled in vitro under various conditions with uridine-5-3H, and the specific activities of the acid-soluble UTP pools were determined by high-pressure liquid chromatography. Essentially, all the acid-soluble counts were in either UTP- or UDP-glucose. The relationship between the intracellular UTP specific activity, the extracellular uridine concentration, and the time of labeling demonstrates that the incorporation of uridine cannot be taken as a direct measure of RNA synthesis in these cells.