Figure 1

Serum triggers an intracellular Ca²⁺ signal. (A) The perfusion of a Ca²⁺-free recording solution containing 5% of serum on Fura-2-loaded MCF-7 cells elicited a strong intracellular Ca²⁺ signal (a). This signal was due to release from IP₃-sensitive Ca²⁺ stores as it was sensitive to previous application of 2-APB (75 μM, b) or XeC (25 μM, c). Furthermore, U-73122 (20 μM) prevented the effect of serum on intracellular Ca²⁺ release (d) whereas the inactive analogue U-73343 (20 μM) was ineffective (d, inset). (B) E₂ (10 nM) triggered intracellular Ca²⁺ elevations in MCF-7 cells perfused with a Ca²⁺-free medium (a); these Ca²⁺ elevations were inhibited by XeC (25 μM, b). In each panel, the results show the typical traces of 27 to 35 cells, always represented at the same scale; each time, also the mean signal is represented (thick black line).