Fig. 2.

Agent effects on intracellular and transferred ascorbate. EA.hy926 cells cultured on filters for 4 days were treated in culture medium above the filters with 300 μM ascorbate and the agents shown at the following concentrations: sulfinpyrazone, 2 mM; 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), 0.3 mM; niflumic acid, 0.3 mM; probenecid, 2 mM; bumetanide, 0.3 mM; forskolin (Fors), 0.1 mM; IBMX, 0.1 mM; and thrombin, 0.15 IU/ml. After 1 h, medium below the cells was sampled for assay of ascorbate (B), and the cells were rinsed 3 times in KRH and taken for assay of intracellular ascorbate (A). Results are shown from 4–5 experiments, expressed as a fraction of the ascorbate concentration found in cells treated only with ascorbate. *P < 0.05 compared with control (indicated by the horizontal dashed line). Absolute values for control samples treated only with ascorbate were as follows: intracellular ascorbate, 3.8 ± 0.2 mM; transferred ascorbate, 34 ± 2.4 μM in the bottom well.