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A simple radiometric assay for methotrexate and other folate antagonists. 1979

R J Hayman, and H Fong, and M B Van der Weyden

A rapid radiometric assay for the folate antagonist MTX, based on the inhibition of chicken liver dihydrofolate reductase activity, has been developed. In the system the inhibition by MTX of the reduction of tritiated FH2 is standardized and used to quantitate this antagonist in plasma of subjects receiving high-dose MTX therapy. The assay permits the detection of plasma MTX levels to 5 X 10(-9)M with a coefficient of variation of 15%. The predominating circulating folate, 5 methyltetrahydrofolate, or the rescue agent leucovorin (5 formyltetrahydrofolate) do not significantly interfere with the assay at concentrations attainable with current rescue programs. Analyses of multiple plasma samples with the present assay show close agreement with the competitive protein-binding assay.

UI MeSH Term Description Entries
D008727 Methotrexate An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA. Amethopterin,Methotrexate Hydrate,Methotrexate Sodium,Methotrexate, (D)-Isomer,Methotrexate, (DL)-Isomer,Methotrexate, Dicesium Salt,Methotrexate, Disodium Salt,Methotrexate, Sodium Salt,Mexate,Dicesium Salt Methotrexate,Hydrate, Methotrexate,Sodium, Methotrexate
D011874 Radiometry The measurement of radiation by photography, as in x-ray film and film badge, by Geiger-Mueller tube, and by SCINTILLATION COUNTING. Geiger-Mueller Counters,Nuclear Track Detection,Radiation Dosimetry,Dosimetry, Radiation,Geiger Counter,Geiger-Mueller Counter Tube,Geiger-Mueller Probe,Geiger-Mueller Tube,Radiation Counter,Counter Tube, Geiger-Mueller,Counter Tubes, Geiger-Mueller,Counter, Geiger,Counter, Radiation,Counters, Geiger,Counters, Geiger-Mueller,Counters, Radiation,Detection, Nuclear Track,Dosimetries, Radiation,Geiger Counters,Geiger Mueller Counter Tube,Geiger Mueller Counters,Geiger Mueller Probe,Geiger Mueller Tube,Geiger-Mueller Counter Tubes,Geiger-Mueller Probes,Geiger-Mueller Tubes,Probe, Geiger-Mueller,Probes, Geiger-Mueller,Radiation Counters,Radiation Dosimetries,Tube, Geiger-Mueller,Tube, Geiger-Mueller Counter,Tubes, Geiger-Mueller,Tubes, Geiger-Mueller Counter
D002645 Chickens Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA. Gallus gallus,Gallus domesticus,Gallus gallus domesticus,Chicken
D002955 Leucovorin The active metabolite of FOLIC ACID. Leucovorin is used principally as an antidote to FOLIC ACID ANTAGONISTS. Calcium Leucovorin,Citrovorum Factor,Folinic Acid,N(5)-Formyltetrahydrofolate,5-Formyltetrahydrofolate,5-Formyltetrahydropteroylglutamate,Calcium Folinate,Folinic Acid-SF,Leucovorin, (D)-Isomer,Leucovorin, (DL)-Isomer,Leucovorin, (R)-Isomer,Leucovorin, Calcium (1:1) Salt,Leucovorin, Calcium (1:1) Salt, (DL)-Isomer,Leucovorin, Calcium (1:1) Salt, Pentahydrate,Leucovorin, Monosodium Salt,Leukovorin,Leukovorum,Wellcovorin,5 Formyltetrahydrofolate,5 Formyltetrahydropteroylglutamate,Acid, Folinic,Factor, Citrovorum,Folinate, Calcium,Folinic Acid SF,Leucovorin, Calcium,Monosodium Salt Leucovorin
D004305 Dose-Response Relationship, Drug The relationship between the dose of an administered drug and the response of the organism to the drug. Dose Response Relationship, Drug,Dose-Response Relationships, Drug,Drug Dose-Response Relationship,Drug Dose-Response Relationships,Relationship, Drug Dose-Response,Relationships, Drug Dose-Response
D005493 Folic Acid Antagonists Inhibitors of the enzyme, dihydrofolate reductase (TETRAHYDROFOLATE DEHYDROGENASE), which converts dihydrofolate (FH2) to tetrahydrofolate (FH4). They are frequently used in cancer chemotherapy. (From AMA, Drug Evaluations Annual, 1994, p2033) Antifolate,Antifolates,Dihydrofolate Reductase Inhibitor,Folic Acid Antagonist,Dihydrofolate Reductase Inhibitors,Folic Acid Metabolism Inhibitors,Acid Antagonist, Folic,Acid Antagonists, Folic,Antagonist, Folic Acid,Antagonists, Folic Acid,Inhibitor, Dihydrofolate Reductase,Inhibitors, Dihydrofolate Reductase,Reductase Inhibitor, Dihydrofolate,Reductase Inhibitors, Dihydrofolate
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013763 Tetrahydrofolates Compounds based on 5,6,7,8-tetrahydrofolate.

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