Figure 5. Induction of the UPR by ABT-737 is associated with increases in cytosolic Ca²⁺.

A. Mel-RM and MM200 cells were treated with ABT-737 for indicated periods. Cells were collected, washed and incubated with 1µM of the fluorescent calcium probe Calcium Green-1 before analysis of calcium levels by flow cytometry. Obatoclax was unable to be used due to the inherent fluorescence of the compound. Increase in mean fluorescence is indicative of an increase in cytosolic calcium. Where indicated, cells were pretreated for 4 hours with 10µM of the calcium chelator BAPTA-AM before addition of ABT-737. Points, mean of three individual experiments; bars, SE.

B. Mel-RM and MM200 cells were treated for 48 hours with Obatoclax (1µM) or ABT-737 (10µM) with or without a 4 hour pretreatnent with various doses of BAPTA-AM. Cells were then subjected to measurement of apoptosis by the propidium iodide method. Columns, mean of three individual experiments; bars, SE.