Fig. 4.

l-ascorbate is specific for CFTR-mediated Cl secretion. (A) Transepithelial Cl currents across nasal CF15 epithelia (ΔF508) and CFTR-corrected CF15 epithelia (+wtCFTR) were measured in the presence of the sodium channel blocker amiloride (20 μM). Gene transfer of WT CFTR recovered the defective Cl secretory response to l-ascorbate (500 μM, mucosal). Ascorbate-stimulated CFTR Cl currents were further activated by forskolin (20 μM) and blocked by DPC (4 mM) in +wtCFTR but no ΔF508. (B) Summary of ascorbate-stimulated Cl currents before (Ascorbate) and after (Ascorbate+Forskolin) addition of forskolin in +wtCFTR vs. ΔF508 epithelia. ^*, Significantly different from ΔF508, P ≤ 0.05; n = 5-7 experiments.