Extracellular signal-regulated kinase1/2 in contraction of vascular smooth muscle.
Smooth muscle contractility is regulated by both intracellular Ca2+ concentration ([Ca2+]i) and Ca2+ sensitivity of the contractile apparatus. Extracellular signal-regulated kinases1/2 (ERK1/2) have been implicated in modulating Ca2+ sensitivity of smooth muscle contraction but mechanisms of action remain elusive. This study investigated the roles of ERK1/2 in modulating [Ca2+]i, calcium sensitivity and the 20-kDa myosin light chain (MLC20) phosphorylation during contraction activated by alpha1-adrenoceptor agonist phenylephrine and thromboxane A2 mimetic U46619 in rat tail artery strips. A specific inhibitor for ERK1/2 activation, U0126, inhibited phenylephrine- and U46619-induced contraction, shifting both concentration-response curves rightward. During phenylephrine-stimulated contraction, U0126 exhibited concentration-dependent inhibition towards force but significant decreases in [Ca2+]i were detected only at higher concentration. Both phenylephrine and U46619 induced a transient activation of ERK1/2 which was abolished by U0126 but unaffected by a general tyrosine kinase inhibitor genistein or Rho kinase inhibitor Y27632 at concentrations inhibiting more than 50% force. Interestingly, U0126 had no effect on steady-state MLC20 phosphorylation levels stimulated by both receptor agonists. These results indicated that during contraction of rat tail artery smooth muscle activated by alpha1-adrenoceptor agonist or thromboxane A2 analogue, ERK1/2 increase Ca2+ sensitivity that does not involve the modulation of MLC20 phosphorylation.
Tsai
Ming-Ho
MH
Institute of Basic Medical Sciences, College of Medicine, National Cheng-Kung University, Tainan 701, Taiwan.
Jiang
Meei Jyh
MJ
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology*; D018994:Myosin Light Chains / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D000577:Amides; D002070:Butadienes; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D018994:Myosin Light Chains; D009570:Nitriles; D011725:Pyridines; C113580:U 0126; C108830:Y 27632; D010656:Phenylephrine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019833:Genistein; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium