title: Application of the isotope-dilution principle to the analysis of factors affecting the incorporation of (3H) uridine and (3H) cytidine into cultured lymphocytes. Evaluation of pools in serum and culture media.
abstract: 1. Rat lymph-node cells were incubated in serum and medium 199 with [5-(3)H]uridine or [5-(3)H]cytidine and acid-precipitable radioactivity was measured. Results were interpreted in terms of an isotope-dilution model. 2. Both serum and medium 199 contained pools that inhibited radioactive labelling in a competitive manner. The serum activity was diffusible and inhibited labelling with [(3)H]cytidine more than with [(3)H]uridine; in these respects the activity resembled cytidine (14mum). 3. The pools in serum and plasma were the same size; however, the rate of labelling was greater in plasma, owing to a diffusible factor. 4. Paradoxically, relatively simple media (Earle's salts and Eagle's minimum essential) appeared to have a larger pool than the more complex pyrimidine-containing medium 199; this suggests a contribution to the pool by cells in the simple media. 5. In the absence of pools the average cell was capable of incorporating 2000 radioactive nucleoside molecules/s.
mesh_terms: D000818:Animals; D001769:Blood; D002478:Cells, Cultured / Q000378:metabolism*; D003470:Culture Media; D003562:Cytidine / Q000097:blood / Q000378:metabolism*; D004058:Diffusion; D005260:Female; D008198:Lymph Nodes / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism*; D008954:Models, Biological; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium; D014529:Uridine / Q000097:blood / Q000378:metabolism*
chemical_list: D003470:Culture Media; D014316:Tritium; D003562:Cytidine; D014529:Uridine