On the action of fluorouracil on leukemia cells.

The uptake and metabolism of radioactive uracil, uridine, phosphate, and 5-fluorouracil by the mouse L1210 leukemic leukocytes and a fluorouracil-resistant variant were investigated. The dual aims of the research were to locate a metabolic differ ence responsible for resistance, and to define the site of action of the inhibitor. The resistant cells possess a much less active "sal vage" pathway, from uracil to nucleic acids, owing to a weaker