Diphenylene iodonium blocks K⁺ and Ca²⁺ currents in type I cells isolated from the neonatal rat carotid body

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.