FIGURE 4.

2-APB activates Ca²⁺ entry and membrane currents in MCF7 cells in the absence of store depletion. A, MDA-MB231 and MCF7 cells were loaded with Fura2 and incubated in an HBSS solution containing 2 mm Ca²⁺ followed by stimulation with 30 μm 2-APB; only MCF7 show a significant Ca²⁺ entry upon 2-APB stimulation (similar results were obtained with 50 μm 2-APB). Using a pipette solution where Ca²⁺ was buffered to the physiological concentration of 100 nm, whole cell recording in MDA-MB231 showed no increase in DVF currents after addition of 50 μm 2-APB (B and C) while MCF7 showed substantial current activation in response to the same concentration of 2-APB (D and E). The I/V curves represented in C and E were taken where indicated by the color-coded asterisks in B and D, respectively.