A Membrane Electrical Mechanism for Hypoxic Vasoconstriction of Small Pulmonary Arteries from Cat

¹ From the Departments of Neurology and Physiology, Medical College of Wisconsin, Milwaukee, and Veterans Administration Medical Center, Wood, Wisconsin

Using specially fabricated muscle myographs, we examined electrical and mechanical responses to reduction of Po₂ in small (<300 µm) pulmonary arteries excised from cat lungs. Upon lowering Po₂ from 400 to 50 mm Hg, these preparations consistently developed contractile responses concomitant with membrane depolarization and action potential generation. The largest changes in electromechanical responses to reduction of Po₂ occurred between 150 and 50 mm Hg. These data strongly suggest that hypoxic activation of small pulmonary arteries is mediated by direct effects of reduced Po₂ on muscle cell membrane ionic conductance systems.