Changes in the pool of deoxyuridine monophosphate in the normal embryogenesis of rats and under the influence of the folic acid antagonist chloridin.

Using the methods of ion exchange and paper chromatography, the content of d-UMP, AMP, GMP, and UMP was measured in 13-15 day rat embryos, and the changes in the pools of these nucleotides under the action of chloridin, one of the inhibitors of dihydrofolate reductase, were also determined. Only the concentration of d-UMP changed appreciably: it increased in the case of normal development from the 13th to the 14th day, apralleling a decrease in the specific activity of TMS, and especially sharply under the action of chloridin, which, inhibiting dihydrofolate reductase, evidently created a deficiency of FA-H4 and thereby blocked the TMS reaction.