Rate of Incorporation of Tritiated Thymidine into DNA of Normoblastic and Megaloblastic Bone Marrow Cells in vitro

Abstract

A normal rate of incorporation of tritiated thymidine (3H-TdR) into the DNA of bone marrow cells was found in 9 iron-deficient patients and 3 patients with chronic liver disease. By contrast, the uptake was significantly depressed in 5 out of 7 patients with vitamin B<sub>12</sub> or folate deficiency, in 2 of 8 patients with megaloblastic changes induced by antipurines and in 2 of 8 patients with a macrocytosis caused by alcoholism. The low rate of uptake of 3H-TdR in the latter 4 cases could not be attributed to an interference with vitamin B<sub>12</sub> or folate metabolism as their marrow cells showed a normal suppression of 3H-TdR uptake after pre-incubation with deoxyuridine. 3 patients with a combination of iron and vitamin B<sub>12</sub> deficiency showed a normal incorporation of 3H-TdR/103 DNA-synthesizing cells, but the mean rate of incorporation in this group was depressed by 50% following iron therapy. These 3 patients also showed a subnormal suppression of 3H-TdR incorporation after incubation with deoxyuridine, and this abnormality was made worse after therapy with iron. These results indicate that the disturbance in DNA synthesis which occurs in vitamin B<sub>12</sub> deficiency is ameliorated by the co-existence of iron deficiency.