Figure 1.

Etoposide and IR induce Cer formation and apoptosis. Jurkat T cells (J16) labeled until equilibrium with [¹⁴C]serine were exposed to etoposide (10 μg/ml) or IR (30 Gy), or left untreated (medium). At the indicated times, Cer levels and apoptosis were determined. (a) TLC separation of Cer from dihydroceramide. Apoptosis is expressed as percentage of nuclei with subdiploid DNA content. (b) Time course of changes in Cer levels induced by etoposide or IR. Cer data are expressed as -fold increase relative to control and are representative of three experiments. The inset shows Cer levels (expressed relative to total radioactivity in phosphatidylserine and phosphatidylethanolamine) at shorter time points. Cer, ceramide; IR, γ-radiation.