| 摘要 |
A radioassay system for the determination of methotrexate in biological fluids based on the competitive binding of labeled and unlabeled methotrexate to the enzyme dihydrofolate reductase. Samples of unknown methotrexate level are mixed with I125 labeled methotrexate. A portion of the total methotrexate present is bound by the addition of enzyme, and the unbound methotrexate is removed with charcoal. The level of bound I125 labeled methotrexate is measured in a gamma ray counter. To calculate the methotrexate level of the unknown samples, the displacement of bound labeled methotrexate caused by the unknowns is compared to the displacement caused by known methotrexate standards. |
