Alteration in the release of endothelium-derived relaxing factors by alpha-adrenoceptor stimulation in the aorta of stroke-prone spontaneously hypertensive rats.
1. Endothelium-dependent relaxation by alpha-adrenoceptor agonists was examined in the thoracic aorta from normotensive Wistar-Kyoto (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP). 2. In ring preparations from both strains, noradrenaline-induced contraction was increased by L-nitro arginine (L-NNA), a NO synthesis inhibitor. 3. L-NNA increased the contraction induced by phenylephrine, an alpha1-adrenoceptor agonist. UK-14304 and clonidine, alpha2-adrenoceptor agonists, did not contract the preparations with intact endothelium. However, these agents contracted preparations when NO synthesis was inhibited. 4. In a precontracted preparation, clonidine and UK-14304 induced relaxations. The relaxations in SHRSP aorta were smaller than those in WKY aorta. 5. These results indicate that alpha-agonists release NO from endothelium in WKY and SHRSP aorta. The mechanism related to NO release by alpha2-adrenoceptor agonist is impaired in SHRSP aorta.
Shimamura
K
K
Research Institute of Hypertension, Kinki University, Ohno-higashi, Osaka-sayama, Japan.
Matsuda
K
K
Yamamoto
K
K
Sunano
S
S
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000503:physiopathology; D002561:Cerebrovascular Disorders / Q000235:genetics / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D009638:Norepinephrine / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000316:Adrenergic alpha-Agonists; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D009638:Norepinephrine