TABLE 19

Inhibition of [³H]dUrd incorporation into DNA in L1210 leukemic cells by MTX and Ara-C alone and in (1:0.782) combination L1210 murine leukemic cells (8 × 10⁶ cells) were incubated in Eagle's basal medium in the presence and absence of various concentrations of MTX and Ara-C and their mixture (molar ratio, 1:0.782) at 37°C for 20 min and then incubated with 0.5 μM (1 μCi) of [6-³H]dUrd at 37°C for 30 min. Fractional inhibition (f_i or f_a) of [6-³H]dUrd incorporation into perchloric acid-insoluble DNA fraction was then measured. All measurements were made in duplicate. Modified from “Quantitative Analysis of Dose-Effect Relationships: The Combined Effects of Multiple Drugs or Enzyme Inhibitors,” Advances in Enzyme Regulation, volume 22, pp 27-55. Copyright 1984 with permission from Elsevier.