Fig. 9. Direct store depletion causes PMN S1P synthesis.

PMN (2 × 10⁶) were incubated with DMS or vehicle as indicated for 10 min. Reactions were started (t = 0) by adding [³H]sphingosine with or without TG (see text). The reactions were stopped at 0, 2, 5, and 10 min. Total [³H]S1P was collected and assayed by TLC. The mean ± S.E. of three observations at each time point is shown. TG initiated rapid synthesis of S1P. No significant S1P synthesis was seen in the absence of TG. DMS abolished S1P production in TG-treated cells to the level of unstimulated cells.