Fig. 10. Role of the cytoskeleton in cell volume changes. Using Fura-2 as a volume marker, cell volume changes were monitored in the presence of substances that affect the assembly of microtubules or actin filaments. (A,B) The tubulin polymerization inhibitors colchicine (25 µmol l^–1) and vinblastine (200 µmol l^–1) had little effect on the cell shrinkage under hypertonic conditions (+85 mmol l^–1 NaCl) but caused an increased swelling under hypotonic conditions (–59 mmol l^–1 NaCl; 5 min each). The effects were abolished in the presence of the tubulin polymerization enhancer paclitaxel (30 nmol l^–1). The simultaneously measured cytosolic Ca²⁺ concentration was hardly affected by the various drugs and/or changes in the extracellular osmolality. (C) Statistical analysis (means ± s.d., number of experiments below data bars) of experiments under hypotonic conditions with colchicine, vinblastine, paclitaxel, and the actin polymerization inhibitors cytochalasine B and D. Cell swelling increased when tubulin polymerization was inhibited (P<0.01) but not when actin polymerization was inhibited.