Effect of shear stress on cytosolic Ca2+ of calf pulmonary artery endothelial cells.
The purpose of the present study was to determine if hemodynamic shear stress increases free cytosolic Ca2+ concentration ([Ca2+]i) of cultured pulmonary artery endothelial cells exposed to steady laminar fluid flow in a parallel plate chamber. Average [Ca2+]i was estimated by measuring cell-associated fura-2 fluorescence using microfluorimetric analysis. To determine [Ca2+]i close to the membrane surface, 86Rb+ efflux via Ca(2+)-dependent K+ channels was measured. Upon initiation of flow or upon step increases in flow, no change in [Ca2+]i was observed using fura-2. However, increases in shear stress produced a large, transient increase in 86Rb+ efflux. The shear stress-dependent increase in 86Rb+ efflux was not blocked by either tetrabutylammonium ions (20 mM) or by charybdotoxin (10 nM), two specific inhibitors of the Ca(2+)-dependent K+ channel of vascular endothelial cells. These results demonstrate that shear stress per se has little effect on either the average cytosolic [Ca2+]i as measured by fura-2 or on [Ca2+]i close to the cytoplasmic surface of the plasmalemma as measured by the activity of Ca(2+)-dependent K+ channels.
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
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Schilling
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Eskin
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D018999:Charybdotoxin; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D005453:Fluorescence; D016257:Fura-2 / Q000494:pharmacology; D007700:Kinetics; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012413:Rubidium / Q000378:metabolism; D012604:Scorpion Venoms / Q000494:pharmacology; D013314:Stress, Mechanical
D015221:Potassium Channels; D000644:Quaternary Ammonium Compounds; D012604:Scorpion Venoms; D018999:Charybdotoxin; C009405:tetrabutylammonium; D012413:Rubidium; D002118:Calcium; D016257:Fura-2