The effect of homocysteine, methionine, serine and glycine on DNA synthesis by human normoblastic and megaloblastic bone marrow cells.

Both glycine and methionine, when added to a suspension of human bone marrow cells, impaired the utilization of deoxyuridine for DNA synthesis, using either the uptake of 3H-deoxyuridine or the subsequent uptake of 3H-thymidine as an index. Homocysteine reduced the uptake of both 3H-deoxyuridine and 3H-thymidine, indicating interference with DNA synthesis after the stage of thymidylate synthesis. Another explanation that the decreased uptake of both substances by homocysteine was due to cell damage caused in vitro was suggested by the trypan blue viability test. Serine generally did not produce significant effects. No difference could be detected between the results in normoblastic and megaloblastic marrow.