Comparison of three radioligands, selenium-75, iodine-125, and tritium, in the radioimmunoassay of methotrexate

Journal Article · Fri Sep 01 04:00:00 EDT 1978 · Clin. Chem.; (United States)

OSTI ID:6453433

Paxton, J W ^[1]; Rowell, F J; Cree, G M

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1. Univ. of Glasgow, Scotland

Radioimmunoassays for methotrexate are described, involving use of a rabbit antiserum to a conjugate of the drug and bovine serum albumin and the drug labeled with tritium, selenium-75, or iodine-125. Of the two gamma emitters, the /sup 75/Se-labeled drug was prepared by the Radiochemical Centre, Amersham, England and the /sup 125/I-labeled drug in the laboratory, by the Chloramine T iodination technique. The stability of labels with both methods allows use of the faster, cheaper, and simpler gamma-counting techniques, with results available after 3 h. All three methods have acceptable sensitivity, accuracy, precision, and reproducibility, and are specific for methotrexate, with no significant interference from naturally occurring folates or leucovorin. The assays in which the gamma emitters are used have significant practical advantages over the beta emitter and are much better suited to automation and clinical application. The main advantage of /sup 75/Se-labeled methotrexate is its longer half-life, 121 days, as compared with 60 days for /sup 125/I.

• OSTI ID: 6453433
• Journal Information: Clin. Chem.; (United States), Journal Name: Clin. Chem.; (United States) Vol. 24:9; ISSN CLCHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ANTIMETABOLITES
ANTIMITOTIC DRUGS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
COMPARATIVE EVALUATIONS
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
EVEN-ODD NUCLEI
HYDROGEN ISOTOPES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGANDS
LIGHT NUCLEI
METHOTREXATE
NUCLEI
ODD-EVEN NUCLEI
RADIOACTIVE MATERIALS
RADIOASSAY
RADIOIMMUNOASSAY
RADIOISOTOPES
RADIOPHARMACEUTICALS
SELENIUM 75
SELENIUM ISOTOPES
TRACER TECHNIQUES
TRITIUM
YEARS LIVING RADIOISOTOPES