[Studies on the mechanism of cytotoxicity of 5-fluorouracil--through impairment of metabolism].

Mechanism of cytotoxicity of 5-fluorouracil (5-FU) in relation to impairment of RNA metabolism was studied. 5-FU depressed the levels of ribonucleotide reductase and thymidine kinase, which are two key enzymes in DNA synthesis, in solid AH-130 tumor when given intraperitoneally at a dose of 60 mg/kg, and this inhibition seemed to be very toxic against cells. But this dose of 5-FU exceeded the amount that could be degraded by the liver, which was much higher than the clinical dose. We concluded that the impairment of RNA metabolism caused by 5-FU played a minor role in its anti-tumor actions.