Activation pathways of 5-fluorouracil in rat organs and in PC12 cells11Abbreviations: PRPP, 5-phosphoribosyl 1-pyrophosphate; 5-FU, 5-fluorouracil; FUrd, 5-fluorouridine; 5-FUMP, 5-FUDP, and 5-FUTP, 5-fluorouridine 5′-mono-, -di-, and -triphosphate, 5-Fdeoxyuridine, 5-fluoro-2′-deoxyuridine; 5-FdeoxyUMP, 5-FdeoxyUDP, and 5-FdeoxyUTP, 5-fluoro-2′-deoxyuridine 5′-mono-, -di-, and triphosphate; Rib1-P, ribose 1-phosphate; and deoxyRib1-P, 2′-deoxyribose 1-phosphate.