Ang-1 induces SK-1 activation in HUVECs. (A) HUVECs were either untreated or treated with Ang-1 at 0.2 μg/mL for various times. Cells were lysed and SK-1 activity measured. Shown are pooled data from 3 experiments and expressed as fold change in relation to untreated group, where the SK-1 activity was normalized to 1.0 (*P < .01 vs untreated group). (B) HUVECs were untreated (Nil) or treated with Ang-1 at 0.2 μg/mL for 15 minutes. Intracellular S1P levels were determined. Data are mean plus or minus SEM from 3 independent experiments (*P < .001 vs untreated group).