Effects of NG-nitro-L-arginine on alpha-agonists-induced contraction of aortae from Wistar Kyoto rats and stroke-prone spontaneously hypertensive rats.
Differences in the influences of endothelium-derived nitric oxside (NO) on alpha-agonists-induced contraction in the aortae of spontaneously hypertensive and normotensive rats were studied by blocking NO synthesis with NG-nitro-L-arginine (L-NNA). L-NNA potentiated the contraction induced by noradrenaline. The potentiation was smaller in the preparation from stroke-prone spontaneously hypertensive rats (SHRSP) than in the preparation from Wistar Kyoto rats (WKY). Similar potentiation was observed in the contraction induced by phenylephrine; the potentiation was also smaller in the preparation from SHRSP. alpha 2-agonists, clonidine and UK-14304 induced dose-dependent contraction only in the presence of L-NNA. The dose-response curves for alpha 2-agonists in SHRSP aorta were different from those in WKY aorta; the maximum tension was observed at the concentration of 10(-6) M in the preparation from WKY, while the contraction further increased up to 10(-4) M in the preparation from WKY. Noradrenaline, clonidine and UK-14304 but not phenylephrine induced relaxation which was blocked by L-NNA. The relaxation was impaired in the preparation from SHRSP in greater extent than that by acetylcholine. It is suggested that basic or noradrenaline-stimulated NO release from endothelium decreased in the preparation from SHRSP and that alpha 2-adrenoceptor of both the endothelium and smooth muscle may be altered in the preparation from SHRSP.
Matsuda
K
K
Research Institute of Hypertension, Kinki University, Osaka, Japan.
Sekiguchi
F
F
Tojo
M
M
Shimamura
K
K
Sunano
S
S
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology; D019335:Nitroarginine; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism
D000316:Adrenergic alpha-Agonists; D018341:Receptors, Adrenergic, alpha-2; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine