Fig. 1. Calcium entry is required for shear-flow-induced cell motility. (A,B) Ax2 cells were allowed to adhere to glass at a low (5-10 µM) calcium concentration, then the calcium concentration was raised to the indicated value by changing the bathing solution at low shear stress. The flow was then stopped and video recording started (t=0 minutes). After 2 minutes, a constant shear flow (2.4 Pa) was applied (arrow). The instant cell speed (A) and directionality (B) are plotted as a function of time. , and : 10 µM, 30 µM and 1 mM CaCl₂, respectively, added to MES-Na buffer. Standard deviations in (A) and (B) are 3 µm minute^-1 and 0.1, respectively (data not shown). (C,D) Cells were allowed to adhere to glass at a low (5 µM) calcium concentration (MES-Na buffer), then a constant shear flow (2.4 Pa) was applied and video recording started (t=0 minutes). (C) At the indicated times, the flowing solution was exchanged, first for MES-Na buffer supplemented with 100 µM EGTA, then for MES-Na buffer supplemented with 1 mM CaCl₂. (D) The same procedure was applied, except that MES-Na buffer was first supplemented with 1 mM CaCl₂, then with 1 mM CaCl₂ + 100 µM GdCl₃. The average instant cell speed <v_i> is plotted as a function of time.