Diphenyleneiodonium, an inhibitor of NOXes and DUOXes, is also an iodide-specific transporter.

NADPH oxidases (NOXes) and dual oxidases (DUOXes) generate O2 (.-) and H2O2. Diphenyleneiodonium (DPI) inhibits the activity of these enzymes and is often used as a specific inhibitor. It is shown here that DPI, at concentrations similar to those which inhibit the generation of O2 derivatives, activated the efflux of radioiodide but not of its analog (99m)TcO4 (-) nor of the K(+) cation mimic (86)Rb(+) in thyroid cells, in the PCCl3 rat thyroid cell line and in COS cell lines expressing the iodide transporter NIS. Effects obtained with DPI, especially in thyroid cells, should therefore be interpreted with caution.