Fig. 5. Buffering free Ca²⁺ inhibited cell volume recovery following hypotonic challenge. At time 0, cells were abruptly exposed to a hypotonic (0.5x) amphibian Ringer, which caused a rapid initial increase in volume followed by a gradual recovery toward basal values. The rate of cell volume recovery was reduced with a low Ca²⁺ hypotonic Ringer solution (5 mM EGTA, n=8, P<0.05 after 40 minutes compared to control values) and by buffering intracellular Ca²⁺ with BAPTA (100 µM, n=8, P<0.05 after 40 minutes compared to control). By contrast, the inhibitory effect of BAPTA was prevented by adding gramicidin (5 µM, n=8) to the extracellular medium (added at 5 minutes, P<0.05 within 5 minutes following addition of ionophore compared to the other three groups). Values are means±s.e.m.