Figure 4.

A change in physiological calcium level induces a volume change. A, C, and E show three endothelial cells in control medium (1.8 mM Ca²⁺). B shows the same cell as in A after exchanging medium with the same calcium level (a positive control). No volume change occurred due to the exchange of media alone. Reducing the extracellular Ca²⁺ from 1.8 mM to 1.6 mM, the volume increased by 28% (compare D with C). Reducing the extracellular Ca²⁺ from 1.8 mM to 1.3 mM, the volume increased by 32% (compare F with E). These data show that the changes of extracellular calcium level in physiological range induce cell volume increase. Scan size: (A and B) 60 μm; (C–H) 50 μm. Effect of MIs on cell volume: images of endothelial cells before (G) and after (H) the addition of MIs, FCCP (10 μM) and dOG (10 mM), in control medium. No volume increase was observed within 10–20 min.