Oxygen-sensing potassium currents in pulmonary artery

The pulmonary vasculature is sensitive to the relative components of the re spiratory gases and will vasoconstrict in response to decreased oxygen (O-2 ) levels. This hypoxic pulmonary vasoconstriction (HPV) controls pulmonary blood flow in the fetus and serves to maximize ventilation perfusion matchi ng in the adult lung. The exact mechanism of HPV is not fully understood bu t it appears to involve direct effects on both the endothelium and smooth m uscle cells within the vessel wall. There is growing evidence to suggest th at hypoxia mediates vasoconstriction, at least in part through the inhibiti on of outward potassium (K+) current in smooth muscle. A number of K+ curre nts present in the pulmonary vasculature have been shown to be sensitive to O-2, with hypoxia acting to inhibit these currents in the majority of case s. Differences in the expression of these O-2-sensitive K+ channels may exp lain regional and generic variations observed in the HPV response. The mech anism by which these K+ channels sense changes in O-2 levels may involve ch anges in the cellular redox state, oxidative phosphorylation or a direct ef fect on the channel protein itself. (C) 1999 Elsevier Science Inc. All righ ts reserved.