Cell swelling increases intracellular calcium in Necturus erythrocytes.

This study examined the role of Ca(2+) in regulatory volume decrease by Necturus erythrocytes. Hypotonic shock (50% tonicity) stimulated an increase in cytosolic free Ca(2+), detected using epi-fluorescence microscopy and the fluorescent Ca(2+) indicator fluo-4-AM (10 microM). A similar increase in fluorescence did not occur under isosmotic conditions, unless cells were exposed to the Ca(2+) ionophore A23187 (0.