Evidence for a PO2-sensitive K+ channel in the type-I cell of the rabbit carotid body.

Type-I cells of rabbit carotid bodies were studied with the patch-clamp technique in the whole-cell and on the cell-attached configuration. Cells exhibiting resting potentials of about -40 mV under normoxic conditions (PO2: 20 kPa), depolarized during hypoxia (PO2: 3.7 kPa). Hypoxia did not affect inward Ca2+ currents but inactivated outward K+ currents in voltage-clamp experiments. Single-channel currents recorded for the cell-attached mode showed a slope conductance of about 137 pS and a 0 mV reversal potential under symmetrical K+ concentration (140 mM). The open-probability (PO) of the single channel was dependent on the extracellular PO2. These data demonstrate the existence of a PO2-sensitive K+ channel in type-I cells, which may account for cell depolarization and the resulting chemosensory response.