Effect of monensin on Dex-induced ceramide generation, aSMase and nSMase, and apoptosis. Thymocytes were treated with Dex (10−7 mol/L) for the indicated times in the presence or absence of monensin (10 μg/mL). (A) Effect of monensin on acidic (on the left) and neutral (on the right) SMase activity induced by Dex treatment for 15 or 120 minutes, respectively. Hydrolyzed SM was quantitated and expressed as picomoles/106 cells. Mean values of three different experiments in duplicate are reported. Standard deviations, less than 5% of the mean values, are omitted for clarity. (B) Ceramide levels in thymocytes treated for 15 minutes with Dex (10−7 mol/L) in the presence or absence of monensin. The quantitative results for ceramide-1-phosphate levels, expressed as picomoles/106 cells, are reported (mean values of three different experiments in duplicate; standard deviations, less than 10% of the mean values, are omitted for clarity). (C) Effect of monensin or bafilomycin A1 (1 μmol/L) on Dex-induced thymocyte apoptosis at 18 hours. Percentage numbers of hypodiploid nuclei are reported for each condition. The results are representative of one out of three separate experiments.
