Acute shear stress does not increase phosphorylation of eNOS at S1179 in mouse mesenteric arteries

Shear stress provokes vasodilation through activation of eNOS, which produces the vasodilator NO·, and is necessary for healthy endothelial function. In cultured endothelial cells, this activation involves increased phosphorylation of eNOS at S1179, and we hypothesized a similar response in intact arteries during shear stress‐induced dilation. Small mesenteric arteries from male mice (7–13 wks old) were cannulated, pressurized (75 mmHg), and one of four treatments was applied: no treatment, phenylephrine (PE, 10 −5 M), PE followed by acetylcholine (ACh, 10 −4 M), or PE followed by high luminal flow (60 μl/min, 15 min); then flash frozen for immunoblotting (4 arteries/group/blot, 2 separate blots). Arteries dilated 65% and 32% in response to ACh and flow, respectively (determined by video microscopy). 45% of the dilation to flow at 60 μl/min is due to NO·, as indicated in separate experiments +/− L‐NAME (n=4/group). eNOS phosphorylation at S1179/total eNOS was 3.85‐fold greater in the ACh group (vs. no treatment), but the high flow group was no greater than the PE group (2.4‐fold and 2.47‐fold, respectively, vs. no treatment), despite robust dilation with flow. These data indicate that PE alone induces phosphorylation of eNOS at S1179 (perhaps through myoendothelial gap junction communication), and increased phosphorylation at this site is not required for shear stress‐induced dilation. APS‐UGSRF and NHLBI‐R15