KATP channels are an important component of the shear-sensing mechanism in the pulmonary microvasculature

Objective: To investigate the role of a K-ATP channel in sensing shear, specifically its cessation, in the endothelial cells of the pulmonary microvasculature. Methods: Endothelial cells isolated from the pulmonary microvasculature of wild-type and K-ATP channel knockout (K(IR)6.2-/-) mice were either statically cultured (non-flow-adapted) or kept under flow (flow-adapted) and the K-IR currents in these cells were monitored by whole-cell patch-clamp technique during flow and its cessation. Membrane potential changes, generation of reactive oxygen species (ROS), and Ca2+ influx with flow cessation were evaluated by the use of fluorescent dyes. Lungs isolated from wild-type mice were imaged to visualize ROS generation in the subpleural endothelium. Results: By patch-clamp analysis, reduction in the K-IR current with cessation of flow occurred only in wild-type cells that were flow-adapted and not in flow-adapted K(IR)6.2(-/-) cells. Similar observations were made using changes in bisoxonol fluorescence as an index of cell membrane potential. Generation of ROS and Ca2+ influx that follow membrane depolarization were significantly lower in statically cultured and in K(IR)6.2(-/-) cells as compared to flow-adapted wild-type cells. Imaging of subpleural endothelial cells of the whole lung showed that the K-ATP antagonist glyburide caused the production of ROS in the absence of flow cessation. Conclusions: The responses to stop of flow (viz. membrane depolarization, K-IR currents, ROS, Ca2+) were significantly altered with knockout of K-ATP channels, which indicates that this channel is an important component of the pulmonary endothelial response to abrupt loss of shear stress.