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Membrane Potential And Na+-K+ Pump Activity Modulate Resting And Bradykinin-Stimulated Changes In Cytosolic Free Calcium In Cultured Endothelial Cells From Bovine Atria, Rachel E. Laskey, David J. Adams, Anthony Johns, Gabor M. Rubanyi, Cornelis Van Breemen

Illawarra Health and Medical Research Institute

The effects of membrane potential on resting and bradykinin-stimulated changes in [Ca2+]i- were measured in fura-2 loaded cultured endothelial cells from bovine atria by spectrofluorimetry. The basal and bradykinin-stimulated release of endothelium- derived relaxing factor, monitored by bioassay methods, were dependent on extracellular Ca2+. Similarly, the plateau phase of the biphasic [Ca2+]i response to bradykinin stimulation exhibited a dependence on extracellular Ca2+, whereas the initial transient [Ca2+], peak was refractory to the removal of extracellular Ca2+. The effect of membrane depolarization on the plateau phase of the bradykinin-induced change in [Ca2+]i- was determined by varying [K+]o. The resting membrane potential …