Hypoxia activates a potassium current in isolated smooth muscle cells from large pulmonary arteries of the rabbit.

Severe hypoxia (< 10 mmHg) induced relaxation of precontracted rings obtained from large diameter (3-4 mm) pulmonary arteries of the rabbit but had no effect upon their basal tone nor upon the length of enzymatically isolated smooth muscle cells. In isolated smooth muscle cells severe hypoxia increased a voltage-gated K+ current. The magnitude of this response depended upon the degree of intracellular Ca2+ buffering, being abolished by 10 mM EGTA. The hypoxic response of K+ currents demonstrates a direct effect of hypoxia on pulmonary artery smooth muscle cells via a modulation of potassium channel activity.