Differential K+ Channel Distribution in Smooth Muscle Cells Isolated from the Pulmonary Arterial Tree of the Rat

Abstract Intracellular photorelease of Ca 2+ demonstrated the presence of Ca 2+ -activated K + channels in smooth muscle cells isolated from different locations of the rat pulmonary arterial tree. However, cell-free patch studies revealed marked differences in K + channel distribution. In the main pulmonary artery the most frequently observed K + channel was a ∼245pS conductance Ca 2+ - and ATP-activated (K Ca,ATP ) channel. In small pulmonary arteries two K + channel types predominated: the K Ca,ATP channel and a ∼185pS conductance K + channel insensitive to intracellular Ca 2+ , ATP and voltage. This difference in K + channel distribution may highlight a more complex regulatory mechanism for controlling membrane potential in small pulmonary arteries, reflecting their physiologically more important role in governing pulmonary vascular reactivity.