Effect of SCF on N-SMase activity in irradiated Ba/F3-Kit cells.

Cells were treated or not with SCF (200 ng/mL for 30 minutes) and irradiated at 4 Gy. Following incubation during the indicated times (as shown in the insert), aliquots (3 × 10⁶ cells/mL) were collected and enzyme assay was performed as described in “Materials and methods” using [choline-methyl-¹⁴C]-SM (60.000 dpm/assay) as substrate. Results are shown at maximum N-SMase stimulation (10-15 minutes after irradiation) and are the mean ± SD of 3 independent experiments (*P < .05). The insert shows N-SMase activity of SCF-treated (○) or untreated (●) Ba/F3-Kit irradiated at 4 Gy that was monitored during a 20-minute period. Results are representative of 3 independent experiments.