Knockdown of Rac1 expression with siRNA did not diminish S1P-induced barrier enhancement of HUVEC or HDMEC monolayers.

<p>A. Time course of changes in TER of HUVEC monolayers before and after treatment with 2 μM S1P or vehicle control, for the Rac1 knockdown and scrambled RNA transfected groups (N = 8 each group). The TER is normalized to the time point just prior to the addition of S1P, for more direct comparisons of the responses to S1P between the groups. <i>B</i>. The mean maximal change in TER of HUVEC monolayers (%) during the first 10 min after S1P was added. The corresponding results for HDMEC monolayers are shown in panels <i>C & D</i> (N = 8 each group). *P<0.05 vs. vehicle control groups; †P<0.05 vs. scrambled RNA sequence group.