Kinase inhibitor screening. (A) BAEC models were pretreated with inhibitors for 1 min at 37°C and stretched (25% elongation) or left unstretched for 5 min in the presence of inhibitors, Na₃VO₄, and ATP. PECAM-1 was immunoprecipitated from solubilized models and immunoblotted with anti–PECAM-1 and 4G10. Note that some inhibitors inhibited PECAM-1 phosphorylation, whereas others did not. Control models were treated with no inhibitor and either Na₃VO₄ or DMSO and Na₃VO₄. Black lines indicate that intervening lanes have been spliced out. (B) Quantification of inhibitor effects on PECAM-1 phosphorylation. Levels of PECAM-1 phosphorylation relative to unstretched models are shown (mean ± SEM; n = 3). Student's t test was used to compare stretched to unstretched samples for each inhibitor. P = 0.0153 (control), 0.0050 (Na₃VO₄), 0.0117 (DMSO), 0.2800 (genistein), 0.2622 (PP2), 0.0958 (SU6656), 0.0158 (Imatinib), 0.0085 (LFM-A13), and 0.0202 (VEGFR inhibitor). *, P < 0.05; **, P < 0.01. (C) BAEC whole cell lysates (total), cell models, and detergent-soluble fractions (soluble) were immunoblotted with anti-Src, anti-Yes, or anti-Fyn. Comparable amounts of total protein were loaded in each lane as shown by immunoblots for actin. (D) Src, Fyn, and Yes were localized to interendothelial contacts in both intact cells and cell models. HAECs were used for Src localization, whereas BAECs were used for Yes and Fyn localization. Bar, 20 μm.