Effects of D600 on hypoxic suppression of K+ currents in isolated type I carotid body cells of the neonatal rat.

K+ currents recorded from isolated type I carotid body cells were reversibly suppressed by hypoxia (pO2 25 Torr). Inhibition of Ca2+ influx using high Mg2+, low Ca2+ solutions abolished this effect, indicating hypoxia selectively inhibits the Ca2(+)-activated component of K+ currents. The Ca2+ channel blockers D600 and verapamil reversed the suppressive effects of hypoxia. These drugs also partially inhibited Ca2(+)-independent K+ currents, but this effect was relieved by hypoxia, causing apparent reversal of hypoxic suppression of the K+ currents seen under control conditions.