Fig. 1.

Removal of extracellular Ca²⁺ inhibits Ca²⁺ waves. A–C: typical records of Ca²⁺ waves recorded in arteriolar smooth muscle cells (SMCs). A: image of a Fluo-4-loaded arteriole with regions of interest (ROIs) used for measuring Ca²⁺ waves shown on 20 SMCs. The ROIs have been colored and enlarged for display purposes. B: Ca²⁺ waves recorded in an arteriole in physiological salt solution (PSS) containing 1.8 mM Ca²⁺ from the 20 ROIs shown in A. C: recordings from 20 ROIs from the same arteriole as in A and B after exposure to nominally Ca²⁺-free PSS (0 mM Ca²⁺ PSS). D and E: pseudocolored images of a Fluo-4-loaded arteriole (average projection of a stack of 500 images cropped to show images of the vessels only) in PSS and in 0 mM Ca²⁺ PSS. F–H: means ± SE (n = 9). F: global Fluo-4 intensity relative to the mean value in PSS (a measure of global myoplasmic Ca²⁺ concentration). G: diameter. H: occurrence (number of waves/cell), amplitude (F/F_o), and frequency (Hz) of Ca²⁺ waves in the presence of 1.8 mM Ca²⁺ (PSS) and after exposure to nominally Ca²⁺-free PSS (0 mM Ca²⁺ PSS). *P < 0.05 compared with PSS via paired t-tests. Scale bars in D and E are 20 μm. F, fluorescence intensity; F_o, baseline fluorescence.