FIGURE 3.

The effects of FTY720 and FB1 on the incorporation of l-[U-¹³C, ¹⁵N]serine into signaling sphingolipids. HPAECs were pretreated with the indicated concentrations of FTY720 or FB1 for 3 h, and then the cells were labeled with l-[U-¹³C, ¹⁵N]serine for 2 h. Label-incorporated sphingoid bases, sphingoid base 1-phosphates, ceramides, and dihydroceramides were quantified by LC/MS/MS. The point of interference for both compounds with sphingolipidde novo biosynthesis is indicated in the scheme (star indicates labeled molecules). **, p < 0.01; ***, p < 0.001 versus control. Palm., palmitoyl; GlyCer, glycosylceramide; SM, sphingomyelin. Error bars represent S.E.