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lüll Ca2+ entry via alpha1G and TRPV4 channels differentially regulates surface expression of P-selectin and barrier integrity in pulmonary capillary endothelium Wu S; Jian MY; Xu YC; Zhou C; Al-Mehdi AB; Liedtke W; Shin HS; Townsley MIAm J Physiol Lung Cell Mol Physiol 2009[Oct]; 297 (4): L650-7Pulmonary vascular endothelial cells express a variety of ion channels that mediate Ca(2+) influx in response to diverse environmental stimuli. However, it is not clear whether Ca(2+) influx from discrete ion channels is functionally coupled to specific outcomes. Thus we conducted a systematic study in mouse lung to address whether the alpha(1G) T-type Ca(2+) channel and the transient receptor potential channel TRPV4 have discrete functional roles in pulmonary capillary endothelium. We used real-time fluorescence imaging for endothelial cytosolic Ca(2+), immunohistochemistry to probe for surface expression of P-selectin, and the filtration coefficient to specifically measure lung endothelial permeability. We demonstrate that membrane depolarization via exposure of pulmonary vascular endothelium to a high-K(+) perfusate induces Ca(2+) entry into alveolar septal endothelial cells and exclusively leads to the surface expression of P-selectin. In contrast, Ca(2+) entry in septal endothelium evoked by the selective TRPV4 activator 4alpha-phorbol-12,13-didecanoate (4alpha-PDD) specifically increases lung endothelial permeability without effect on P-selectin expression. Pharmacological blockade or knockout of alpha(1G) abolishes depolarization-induced Ca(2+) entry and surface expression of P-selectin but does not prevent 4alpha-PDD-activated Ca(2+) entry and the resultant increase in permeability. Conversely, blockade or knockout of TRPV4 specifically abolishes 4alpha-PDD-activated Ca(2+) entry and the increase in permeability, while not impacting depolarization-induced Ca(2+) entry and surface expression of P-selectin. We conclude that in alveolar septal capillaries Ca(2+) entry through alpha(1G) and TRPV4 channels differentially and specifically regulates the transition of endothelial procoagulant phenotype and barrier integrity, respectively.|Animals[MESH]|Calcium Channels, T-Type/*metabolism[MESH]|Calcium Signaling[MESH]|Calcium/*metabolism[MESH]|Carcinogens/pharmacology[MESH]|Endothelium, Vascular/cytology/drug effects/*metabolism[MESH]|Immunoenzyme Techniques[MESH]|Mice[MESH]|Mice, Knockout[MESH]|P-Selectin/*metabolism[MESH]|Phorbol Esters/pharmacology[MESH]|Pulmonary Artery/metabolism[MESH]|TRPV Cation Channels/*metabolism[MESH] |