Dex-induced apoptosis is dependent on caspase activation, an event downstream Dex/GC receptor binding and PI-PLC/aSMase pathway induction. (A) Effect of the caspase inhibitor, Z-VAD-FMK (50 μol/L), on Dex-induced apoptosis, analyzed after 18-hour culture. Percentage numbers of hypodiploid nuclei are reported for each condition. The results are representative of one out of three separate experiments. (B) Thymocytes were treated for 8 hours at 37°C with Dex (10−7 mol/L) in the presence or absence of RU486 (10−6 mol/L), U73122 (2.5 μmol/L), or bafilomycin A1 (1 μmol/L). Crude cell lysates were then assayed for CPP32/Caspase 3 activity by using a colorimetric assay based on spectrophotometric detection of the chromophore pNA after cleavage from the labeled substrate DEVD-pNA. Caspase activity is expressed as nanomoles pNA/106 cells. The results are the mean values of two determinations (standard deviation < 2%). The results are representative of one out of three separate experiments.
