Abstract
Eukaryotic elongation factor 2 (eEF2) kinase (eEF2K) inhibits protein translation through the phosphorylation of its specific substrate, eEF2. We previously demonstrated that eEF2K expression increases in superior mesenteric artery from spontaneously hypertensive rats (SHR) and that eEF2K mediates development of hypertension in SHR. In addition, we recently revealed that A484954, a selective eEF2K inhibitor induced relaxation via opening smooth muscle inward rectifier K+ (Kir) channel in rat isolated superior mesenteric artery. Here, we further examined the effects of A484954 on contractility and blood pressure (BP) in rats. Isometric contraction of rat isolated superior mesenteric artery was measured. BP was measured by a carotid cannulation method. A484954 (10 µM) inhibited noradrenaline (NA)-induced contraction in a biphasic manner (magnitude of inhibition higher at high dose NA). A484954 also inhibited an α1-receptor agonist, phenylephrine-induced contraction, while it was not biphasic. Specifically, a β-receptor antagonist, propranolol (1 µM) prevented the A484954-mediated inhibition of NA (high-dose)-induced contraction. A484954 (10 µM) potentiated a β-receptor agonist, isoproterenol-induced relaxation, which was completely prevented by BaCl2 (1 mM), a Kir channel blocker. In vivo, A484954 (122 µg/kg) inhibited NA-induced increase of BP in rats. Another eEF2K inhibitor, NH125 (22 µg/kg) also inhibited the NA-induced BP increase in rats. In summary, it was concluded that A484954 lowers NA-induced BP rise perhaps through activation of β2-receptor-Kir channel and subsequent vasorelaxation via inhibiting eEF2K activity.