Pyrimidine metabolism in human leukocytes. II. Metabolism of the thymine nucleotide pools in normal and leukemic leukocytes.

subsequent 20 min. The time to reach maximal incorporation of TdR-3H into the thymidine monophosphate (TMP) pool was slower than into the TDP and TTP pools. In leukemic cells the rate of equilibration of TMP with TdR-3H was related directly to the TdR concentration and inversely to the temperature. With increasing concentrations of TdR, expansion of the TMP pool derived from TdR was greater than expansion of the TDP and TTP pools. In leukemic leukocytes the TDP and TTP pools were approximately equal in size and accounted for 65% of the thymine nucleotides in the presence of 1 ¿IMTdR but only 10% in the presence of 300 ¿IMTdR. In normal leukocytes at these TdR concentrations the TDP and TTP pools accounted for 35% and 5% of the total thymine nucleotides. Over the range of TdR concentrations studied, incorporation of TdR-3H into the TMP pool was 2to 5-fold greater and in corporation into the TDP and TTP pool was 6to 15-fold greater in CML than in normal leukocytes. Incorporation of 3 JUM TdR-3H into DNA was 30-fold greater in CML than in normal