Figure 3.

Bcl-2-Induced Inhibition of Ca²⁺ Extrusion Is Responsible for Higher Levels of Necrosis When Cells Are Stressed by Raised External [Ca²⁺] and/or by Menadione

(A) Results of cell death assays performed on WT pancreatic acinar cells. Light green bars represent live cells, blue bars represent apoptotic cells, and red bars represent necrotic cells. The chart is separated into four treatment groups, from the left: untreated control cells, cells treated with 5 mM Ca²⁺, cells treated with 30 μM menadione, and cells treated with both 30 μM menadione and 5 mM Ca²⁺. Error bars in (A), (B), and (E) represent SEM.

(B) Results of cell death assays performed on Bcl-2 KO pancreatic acinar cells. The chart is structured in the same way as in (A), which allows comparison of the differences between WT and Bcl-2 KO cells. Cells lacking Bcl-2 undergo more apoptosis and less necrosis as compared to WT cells when challenged with 30 μM menadione or both menadione and high Ca²⁺.

(C) Typical [Ca²⁺]_i responses to 5 mM Ca²⁺ (green, n_WT = 18), 30 μM menadione in 1 mM Ca²⁺ solution (blue, n_WT = 23), and 30 μM menadione in 5 mM Ca²⁺ (red, n_WT = 22) in WT pancreatic acinar cells. Black arrow shows time point when treatment was applied.

(D) Typical [Ca²⁺]_i responses to 5 mM Ca²⁺ (green, n_Bcl-2 = 12), 30 μM menadione in 1 mM Ca²⁺ solution (blue, n_Bcl-2 = 14), and 30 μM menadione in 5 mM Ca²⁺ (red, n_Bcl-2 = 12) in Bcl-2 KO pancreatic acinar cells. Black arrow shows time point when treatment was applied.

(E) The responses depicted in (C) and (D) were quantitatively analyzed and shown as the average [Ca²⁺]_i responses above the baseline recorded between 200 and 1,200 s and then normalized to the average value of responses to 5 mM Ca²⁺ in WT cells. Green bars represent cells treated with 5 mM Ca²⁺, blue bars represent cells treated with 30 μM menadione, and red bars represent cells treated with both 30 μM menadione and 5 mM Ca²⁺. Responses of WT cells to menadione were greater than those recorded in Bcl-2 KO cells and were additionally potentiated by high extracellular Ca²⁺.