Diphenylene Iodonium Blocks K+ and Ca2+ Currents in Type I Cells Isolated from the Neonatal Rat Carotid Body

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Diphenylene iodonium (DPI), an inhibitor of NAD(P)H oxidase, blocks hypoxic excitation of the carotid body. We use the whole-cell patch-clamp technique to investigate the actions of DPI on ionic currents in isolated type I carotid body cells. DPI (10 μM) caused reversible blockade of K+ and Ca2+ currents in these cells, indicating that DPI is a non-selective ion channel blocker. Since hypoxic excitation of the carotid body is dependent on Ca2+ influx into type I cells, our observation that DPI blocks Ca2+ currents in type I cells can account for the ability of this compound to inhibit hypoxic excitation of the intact organ.