ION CHANNELS, OXYGEN SENSATION AND SIGNAL-TRANSDUCTION IN PULMONARY ARTERIAL SMOOTH-MUSCLE

In contrast to systemic arteries those of the pulmonary circulation co nstrict in response to hypoxia: a mechanism known as ''hypoxic pulmona ry vasoconstriction'' (HPV). It is has been established that changes i n alveolar oxygen tension are the primary stimulus for triggering HPV. The mechanisms underlying this unique response are unknown. Neither t he role of the endothelium nor that of the smooth muscle of the pulmon ary arteries in oxygen sensing has been elucidated, although both tiss ues may be involved. Evidence is accumulating to suggest that K+ chann els located in the plasma membranes of pulmonary arterial smooth muscl e cells may play an important role in oxygen sensing. This process may involve novel mechanisms of signal transduction and K+ channel regula tion by charged intermediates, redox reactions or membrane-delimited f actors.