Figure 2. Naltriben induces Ca²⁺ influx, which might account for reduction in U87 cell viability.

(A) Summary chart of MTT assays, which were used to evaluate U87 cell viability. Cells were treated with vehicle (0.1% DMSO; control; n = 24) or with naltriben (25–100 μM; n = 18) for 24 h. **** represents p < 0.0001 (1-way ANOVA; compared with control). (B) Fura-2 ratiometric Ca²⁺ imaging experiments. U87 cells were pre-loaded with Fura-2 AM (2 μM) in the dark for 30 min at room temperature. Fura-2 Ca²⁺ signal was acquired at alternate excitation wavelengths of 340 and 380 nm. [Top] Representative raw images of U87 cells before (resting basal), during (start naltriben application; continue naltriben application), and after (naltriben peak) application of 50 μM naltriben. White scale bars represent 25 μm. Signal intensity color bar represents the 340/380 ratio. [Bottom Left] Representative 340/380 trace of Fura-2 ratiometric Ca2+ imaging experiments (1 is first application of 50 μM naltriben, 2 is second application of naltriben after wash). [Bottom Right] Summary chart of Fura-2 Ca²⁺ imaging experiments showing no significant difference between the Ca²⁺ responses of the initial exposure to naltriben (n = 24) and the subsequent perfusion following washout (n = 21).