Influence of diphtheria toxin on ceramide metabolism in U-937 cells.

Cells were seeded in 6-well plates and treated with toxin (37.5 ng/mL) for the times indicated, in medium containing [³H]palmitic acid. Total cellular lipids were extracted and analyzed for [³H]sphingomyelin and [³H]ceramide by TLC. Minus toxin controls were run at each time point. Data, shown as percent of control, were calculated from disintegrations per minute (dpm) tritium in sphingomyelin or ceramide per 500 000 dpm total lipid. n = 3 ± SD for each experimental point.