Differential effects of the protease inhibitors zVAD and calpain inhibitor III on mitochondrial calcium content and cell death in 32D and C2 cells. (A) 32D and C2 cells were treated with VP-16 or preincubated for 1 hour with 50 μM zVAD followed by VP-16. After 18 hours of incubation cells were loaded with 1 μM Rhod-2 and analyzed by flow cytometry on the FL-2 channel. Untreated cells are presented as the filled histograms and treated as the open histograms. Histograms representative of 3 independent experiments are shown. (B) Cells were treated with VP-16 or preincubated for 1 hour with various concentrations of zVAD or calpain inhibitor III (as indicated). After 18 hours, cell viability was analyzed by PI uptake on the FL-2 channel. Percentage of PI⁺ (% cell death) cells is shown as the mean ± SD of 3 independent experiments. *P < .05; **P < .005 versus VP-16–treated group (Student t test).