Ion channels, oxygen sensation and signal transduction in pulmonary arterial smooth muscle.

In contrast to systemic arteries those of the pulmonary circulation constrict in response to hypoxia: a mechanism known as "hypoxic pulmonary vasoconstriction" (HPV). It is has been established that changes in alveolar oxygen tension are the primary stimulus for triggering HPV. The mechanisms underlying this unique response are unknown. Neither the role of the endothelium nor that of the smooth muscle of the pulmonary arteries in oxygen sensing has been elucidated, although both tissues may be involved. Evidence is accumulating to suggest that K+ channels located in the plasma membranes of pulmonary arterial smooth muscle cells may play an important role in oxygen sensing. This process may involve novel mechanisms of signal transduction and K+ channel regulation by charged intermediates, redox reactions or membrane-delimited factors.