The modulation of vascular ATP-sensitive K+ channel function via the phosphatidylinositol 3-kinase-Akt pathway activated by phenylephrine.
The present study examined the modulator role of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway activated by the alpha-1 adrenoceptor agonist phenylephrine in ATP-sensitive K(+) channel function in intact vascular smooth muscle. We evaluated the ATP-sensitive K(+) channel function and the activity of the PI3K-Akt pathway in the rat thoracic aorta without endothelium. The PI3K inhibitor 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002) (10(-5) M) augmented relaxation in response to the ATP-sensitive K(+) channel opener levcromakalim (10(-8) to 3 x 10(-6) M) in aortic rings contracted with phenylephrine (3 x 10(-7) M) but not with 9,11-dideoxy-11alpha,9alpha-epoxy-methanoprostaglandin F(2alpha) (U46619; 3 x 10(-8) M), although those agents induced similar contraction. ATP-sensitive K(+) channel currents induced by levcromakalim (10(-6) M) in the presence of phenylephrine (3 x 10(-7) M) were enhanced by the nonselective alpha-adrenoceptor antagonist phentolamine (10(-7) M) and LY294002 (10(-5) M). Levels of the regulatory subunits of PI3K p85-alpha and p55-gamma increased in the membrane fraction from aortas without endothelium treated with phenylephrine (3 x 10(-7) M) but not with U46619 (3 x 10(-8) M). Phenylephrine simultaneously augmented Akt phosphorylation at Ser473 and Thr308. Therefore, activation of the PI3K-Akt pathway seems to play a role in the impairment of ATP-sensitive K(+) channel function in vascular smooth muscle exposed to alpha-1 adrenergic stimuli.
Haba
Masanori
M
Department of Anesthesiology, Wakayama Medical University, Wakayama, Japan.
Hatakeyama
Noboru
N
Kinoshita
Hiroyuki
H
Teramae
Hiroki
H
Azma
Toshiharu
T
Hatano
Yoshio
Y
Matsuda
Naoyuki
N
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D054086:KATP Channels / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D010656:Phenylephrine / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010766:Phosphorylation; D021122:Protein Subunits / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction
D054086:KATP Channels; D021122:Protein Subunits; D010656:Phenylephrine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt