Dynamics of the Ca²⁺ depletion waves.

A) Heat map generated from the time-lapse fluorescence microscopy movie (10 s intervals) of rat SMCs treated with ET-1 (100 nM) in nominally free extracellular Ca²⁺, showing that the SR depletion wave expands in a near circular fashion in both directions of the scan line (dotted white line). B) Average travel distance and velocity of ET-1-induced depletion wave vs. time. As the distance from the point of origin increases, the wave velocity decreases asymptotically to zero. C) Average values for R/R₀ and [Ca²⁺]_SR at the rim of the depletion wave also decreases as the wave expands over time (ROI = 5, n = 5 independent experiments, mean ± SEM, P<0.005).