S1P caused initial endothelial barrier enhancement is concentration-dependent manner.

<p><i>A</i>. Maximal change in TER (%) from baseline within the initial 10-min time window after addition of the indicated concentrations of S1P. *P<0.05 versus vehicle treated group. <i>B</i>. Comparison of representative tracings of TER of HUVEC monolayers treated with 1 μM or 10 μM S1P. After the initial increase in TER, with higher concentrations of S1P (10 μM shown here), this elevated TER is typically short-lived and often decreases to a level below the initial baseline.