Overexpression of WT or DN Rac1 in HUVEC or HDMEC did not alter S1P-induced endothelial barrier enhancement.

<p><i>A</i>. Time course of TER of HUVEC monolayers transfected with WT and DN Rac1 plasmids, treated with either 2 μM S1P or vehicle (N = 8 each group). The TER is normalized to the time point just prior to addition of S1P for a more direct comparison of the magnitude of the response. <i>B</i>. The mean maximal change in TER (%) of HUVEC monolayers in the 10-min window immediately following S1P treatment. The corresponding data for HDMEC monolayers are shown in panels <i>C & D</i> (N = 8 each group). *P<0.05 vs. Vehicle treated groups.