Prolonged peak elevations in cytoplasmic free @entity460 ions, derived from intracellular stores, correlate with the extent of XXXX -stimulated exocytosis in single @entity1 umbilical vein endothelial cells.

@entity1 @entity556 @entity535 @entity2881 @entity8729 @entity460 @entity141 @entity2880
We have used indo-1-loaded @entity1 endothelial cells (EC) in monolayer culture and quantitative laser scanning fluorescence microscopy techniques to investigate the magnitude and duration of the change in cytoplasmic free @entity460 ([ @entity141 ]i) required for @entity556 -stimulated @entity2880 factor ( @entity2881 ) secretion in individual EC. Both alpha- @entity556 and a 14 @entity535 @entity556 receptor activating peptide stimulate an increase in EC [ @entity141 ]i that is agonist dose dependent. Low-dose agonist treatment generates asynchronous oscillations (i.e., repetitive spikes < 80 sec duration) in [ @entity141 ]i. Stimulation with higher agonist concentrations generates a prolonged single peak elevation in [ @entity141 ]i. Both the number of cells displaying prolonged [ @entity141 ]i peaks and the mean amplitude of the peaks increase as a function of agonist concentration. Higher doses of agonist also cause sustained elevations in [ @entity141 ]i that depend upon extracellular @entity141 . Oscillations in [ @entity141 ]i are not sufficient to stimulate significant @entity2881 secretion, and sustained elevations in [ @entity141 ]i are not required for maximal secretion. Both the number of cells displaying prolonged peaks and the mean peak amplitude correlate with increasing levels of @entity2881 secretion from the culture. We have used the expression of @entity8729 , a secretory granule membrane protein, as a marker for measuring @entity556 -induced exocytosis in individual EC. Both the number of secreting cells and the amount of secretion per cell increase as a function of @entity556 concentration. The graded responses in [ @entity141 ]i amplitudes and the graded exocytotic response may be causally related.
