Fig. 4.
GM-CSF increases the transport of dehydroascorbic acid by HL-60 neutrophils. (A) Time-course of the effect of GM-CSF. Cells were incubated for varied times in the absence (○) or in the presence (•) of 0.5 nmol/L GM-CSF before measuring the uptake of dehydroascorbic acid (DHA). Data represent the average of two experiments with three replicates each. (B) Dose-response of the effect of GM-CSF. Cells were incubated for 30 minutes in the presence of different concentrations of GM-CSF and uptake of dehydroascorbic acid was measured afterwards. Data represent the mean ± SD of four samples and correspond to one of three similar experiments. (C) Effect of GM-CSF on the transport of dehydroascorbic acid. Cells were incubated for 30 minutes in the absence (○) or in the presence (•) of 0.5 nmol/L GM-CSF and transport of dehydroascorbic acid was measured afterwards. Data represent the average of two experiments with three replicates each. (D) Double reciprocal plot of the effect of GM-CSF on the substrate dependence for dehydroascorbic acid transport. Cells were incubated for 30 minutes in the absence (○) or in the presence (•) of 0.5 nmol/L GM-CSF and transport of dehydroascorbic acid was measured for 30 seconds. Data represent the mean of four samples and correspond to one of three similar experiments.