Intracellular analog triphosphate production. CEM cells and CEM/ara-G cells were incubated for 6 h with 10 μM ara-C (a) or F-ara-A (b), followed by extraction of the nucleotide pool and measurement of intracellular analog triphosphate concentrations by using HPLC. P = 0.026 for CEM versus CEM/ara-G for ara-CTP production by unpaired T test (a). P = 0.001 for CEM versus CEM/ara-G for F-ara-ATP production by unpaired T test (b). The values shown are the means ± SD of at least three independent experiments.