Fig 3.

Inhibitory effect of NBMPR on ribavirin uptake, accumulation, and anti-HCV activity. The ribavirin concentration used in these experiments (A to C) was 100 μM or 1 mM, while the NBMPR concentrations used were 0.1, 1, 3, 10, 31, and 100 μM. (A) The effect of NBMPR on ribavirin uptake by OR6 cells was analyzed in Na⁺-free KHB with NBMPR. Each value is the mean ± SD from five independent experiments, each performed in duplicate. (B) The effect of NBMPR on ribavirin accumulation in OR6 cells was analyzed by measuring the level of the drug within the cells, in the presence of NBMPR, for 48 h. Each value is the mean ± SD from three independent experiments, each performed in duplicate. (C) The effect of NBMPR on the anti-HCV activity of ribavirin in OR6 cells was analyzed by measuring the level of the luciferase activity, in the presence of NBMPR, for 48 h. The value of relative luciferase activity without ribavirin and NBMPR was set to 100%. Each value is the mean ± SD from three independent experiments, each performed in triplicate. (D) The concentration dependency of ribavirin antiviral action in the presence of NBMPR was examined. The ribavirin concentrations used are shown in the legend to Fig. 1A. The NBMPR concentration was set to 7 μM, which is near the EC₅₀ of NBMPR calculated from the results in panel A. The value of relative luciferase activity in the absence of ribavirin was set to 100%. (E) The time dependency of ribavirin antiviral action in the presence of NBMPR was then examined. The ribavirin concentration was set to 150 μM, while the NBMPR concentration was still 7 μM. The value of relative luciferase activity in the absence of ribavirin at each time point was set to 100%.