Effects of hypoxia/reoxygenation (H/R) on smooth muscle contractility and AMPK phosphorylation in rat aortic smooth muscle ex vivo. Endothelium-denuded rat aortic rings were maintained under normoxic or H/R conditions as described under ‘Materials and methods’. A–B) The changes in Emax and pEC50 values for 5-HT-induced contractions were determined. The data shown are the mean ± SEM values obtained with aortic rings from 3 rats. ##p < 0.01, ###p < 0.001 compared with control (+ 5-HT, Norm); **p < 0.01 compared with 0 mM D-glucose (+ 5-HT, H/R). The changes in AMPKαThr172 phosphorylation were then determined. The representative immunoblots for phospho-AMPKαThr172, AMPKα, and β-actin are shown in panel C.