Fig. 8. Sites of Ca²⁺ wave initiation in unstressed (A-D) and stressed (E-H) cells. Primary endothelial cells were either cultured on coverslips (unstressed) or exposed to a fluid shear stress of 20 dynes/cm² (stressed) from the right to the left for 24 hours in a parallelplate flow chamber. Both sets of cells were loaded with the Ca²⁺ sensing dye Indo-1 (5 µM) before incubating the cells in the presence of either 0.5 µM ATP (unstressed cells) or 2 µM ATP (stressed cells). Images were taken at 0.38 second intervals of a representative cell to visualize Ca²⁺ release. At the end of the recording, the coverslip was fixed and processed to localize caveolin-1 and actin. Cell morphology was used to match Ca²⁺ release with caveolin-1 and actin staining. Bar, 20 µm.