Deoxyuridine suppression test: a comparison of two methods and effect of thymidine on the incorporation of 3H-deoxyuridine into DNA in human bone marrow cells

Deoxyuridine suppression tests have been performed by two different methods of six normoblastic and eight megaloblastic marrows. A good correlation was obtained between the results by the modified and the original methods. The simplified method was found to be applicable for a clinical purpose to diagnose megaloblastosis in the marrow. Uptake of 3H-deoxyuridine into DNA and effect of various concentrations of thymidine was studied on five normoblastic and six megaloblastic marrows. In megaloblastic marrows, a greater amount of thymidine was required to obtain the same rate of suppression of 3H-deoxyuridine incorporation into DNA than in normoblastic marrows. Impairment of thymidine incorporation into DNA in megaloblastic marrows was not revealed. Therefore, lower rate of suppression of 3H-deoxyuridine by thymidine in megaloblastic marrows may be due to impairment of the incorporation of deoxyuridine before the addition of thymidine.