Abstract
Acute inhibition of nitric-oxide synthase (NOS) unmasks the release of endothelium-derived contracting factors (EDCFs). The present study investigated whether chronic inhibition of NOS modulates endothelium-dependent contractions. Eighteen-week-old male Sprague-Dawley rats were treated by daily gavage for 6 weeks with the NOS inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) (60 mg/kg) or vehicle (distilled water; 1 ml/kg). Chronic treatment with l-NAME increased arterial blood pressure. Isometric tension was measured in aortic rings with or without endothelium. Endothelium-dependent relaxations to acetylcholine and the calcium ionophore 5-(methylamino)-2-[(2R,3R,6S,8S,9R,11R)-3,9,11-trimethyl-8-[(1S)-1-methyl-2-oxo-2-(1H-pyrrol-2-yl)-ethyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-4-benzoxazolecarboxylic acid (A23187) were reduced in preparations from l-NAME-treated rats. The reduction in relaxation to A23187 was partially reversed by l-arginine (1 mM). In quiescent aortic rings, A23187 caused contractions in the presence of l-NAME and intact endothelium. The A23187-induced contractions were greater in rings from the l-NAME-treated rats than in those from the control group. These contractions were abolished by the cyclooxygenase (COX)-2 inhibitor N-[2-cyclohexyloxy-4-nitrophenyl]methanesulfonamide (NS-398) and the thromboxane-prostanoid (TP) receptor antagonist 3-((6R)-6-{[(4-chlorophenyl)sulfonyl]amido}-2-methyl-5,6,7,8-tetrahydronaphthalen-1-yl)propanoate (S18886), but not by the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole (SC-560). Chronic l-NAME treatment reduced the level of nitric oxide in the plasma but increased COX activity in the aortic rings. Western blotting and immunohistochemical staining showed that endothelial NOS expression was reduced in the aortae of the chronic l-NAME-treated group. COX-1 expression was augmented slightly, whereas COX-2 expression was up-regulated markedly. The TP receptor expression was comparable with control. These experiments demonstrate that chronic NOS inhibition increases endothelium-dependent contractions of the rat aorta by inducing COX-2 expression and augmenting the production of EDCF.
Footnotes
This study was supported by the Research Grant Council of Hong Kong [Grant University of Hong Kong 7681/06M].
These data are a part of dissertation work: Qu C (2008) Modulation of Endothelium-Dependent Contractions by Chronic Inhibition of Nitric Oxide Synthase in the Rat Aorta, M.Phil. dissertation, University of Hong Kong, Hong Kong.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.167098
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- NOS
- nitric-oxide synthase
- A23187
- 5-(methylamino)-2-[(2R,3R,6S,8S,9R,11R)-3,9,11-trimethyl-8-[(1S)-1-methyl-2-oxo-2-(1H-pyrrol-2-yl)-ethyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-4-benzoxazolecarboxylic acid
- COX
- cyclooxygenase
- EDCF
- endothelium-derived contracting factor
- eNOS
- endothelial nitric-oxide synthase
- l-NAME
- Nω-nitro-l-arginine methyl ester
- NO
- nitric oxide
- NS-398
- N-[2-cyclohexyloxy-4- nitrophenyl]methanesulfonamide
- S18886
- 3-((6R)-6-{[(4-chlorophenyl)sulfonyl]amido}-2-methyl-5,6,7,8-tetrahydronaphthalen-1-yl)propanoate
- SC-560
- 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole
- SHR
- spontaneously hypertensive rat
- TP
- thromboxane-prostanoid
- U46619
- 9,11-dideoxy-9α,11α-methanoepoxy prostaglandin F2α
- PGF
- prostaglandin F
- TBS-T
- Tris-HCl-buffered saline with 0.1% Tween 20.
- Received February 22, 2010.
- Accepted May 4, 2010.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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