Methotrexate Displacement in Man*

Abstract

In a number of mammalian species, including man, the 4-amino analogs of pteroylglutamate persist in liver and kidney for many months af- ter administration (1-4). In the rat (3) and mouse (4), the binding site appears to be the en- zyme dihydrofolate reductase [also termed folate reductase ( Studies with partially purified dihydro- folate reductase obtained from several sources (6-8) have shown the affinity of this enzyme for the 4-amino analogs to be extremely high.