Stretch-induced PECAM-1 phosphorylation in the cell model. (A) BAEC models were stretched or left unstretched for 5 min in the presence or absence of ATP. PECAM-1 was immunoprecipitated from solubilized models and immunoblotted with 4G10 and anti–PECAM-1. An example of typical immunoblotting data is shown (left). Intensity of immunoblotted bands was quantified and expressed relative to the PECAM-1 phosphorylation level in ATP-treated unstretched samples (right; mean ± SEM; n = 4). Student's t test was used to compare stretched to unstretched samples for each category. *, P = 0.0003; #, P = 0.1248. (B) BAEC models were stretched for 5 min to various extents (% elongation) and immunoprecipitated PECAM-1 was immunoblotted with 4G10 and anti–PECAM-1. Levels of phosphorylation were quantified and expressed relative to the PECAM-1 phosphorylation level in unstretched cells (mean ± SEM). Sample size: n = 3 for 0, 5, 15, and 25%; n = 2 for 10 and 20%. Student's t test was used to compare stretched to unstretched samples. *, P = 0.0095, 0.0095, and 0.0049 for 5, 15, and 25%, respectively. (C) Cyclic stretch (15%; 1 Hz; 5 min) induced a 1.53 ± 0.05-fold increase (mean ± SEM; n = 3) of PECAM-1 phosphorylation in extracted BAEC models. Control chambers were left on the movable shaft of the stretch apparatus without stretching so that they were exposed to the same oscillation (motion control). Student's t test was used to compare stretched to unstretched samples. P = 0.0002. (D) Stretch-induced PECAM-1 phosphorylation in intact and extracted HUVEC. Student's t test was used to compare stretched to unstretched samples. In intact cells, stretch induced a 1.42 ± 0.18-fold increase (mean ± SEM; n = 5; P = 0.0273). In extracted models, stretch induced a 1.75 ± 0.33-fold increase (mean ± SEM; n = 5; P = 0.0260). Black lines indicate that intervening lanes have been spliced out.