None of the above. Superoxide dismutase converts superoxide radicals to hydrogen peroxide and O 2 . Ferritins are responsible for binding transition metal ions, such as ferrous iron, thus preventing them from generating oxygen radicals. All of the above are true. Both tumor cells and normal cells are rescued.
Bone marrow is especially sensitive to methotrexate toxicity and is the prime target for rescue.
Leucovorin only needs to be given for a short period of time because methotrexate is rapidly cleared and will be below toxic concentrations in less than 24 hours. The products of leucovorin metabolism are relatively nontoxic. None of the above. They show no sequence specificity. They unwind DNA, hence altering the strain in DNA which can result in conformational changes.