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      Chronic Angiotensin-Converting Enzyme Inhibition and Angiotensin II Type 1 Receptor Blockade : Effects on Cardiovascular Remodeling in Rats Induced by the Long-term Blockade of Nitric Oxide Synthesis

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          Abstract

          Abstract We have shown previously that angiotensin-converting enzyme (ACE) inhibitors prevent coronary vascular remodeling (medial thickening and perivascular fibrosis) and myocardial remodeling (fibrosis and hypertrophy) in rats induced by long-term inhibition of nitric oxide (NO) synthesis with oral administration of N ω -nitro- l -arginine methyl ester (L-NAME). ACE inhibitors inhibit both the formation of angiotensin II and the catabolism of bradykinin. In this study, we aimed to determine the relative contribution of the latter two mechanisms to the beneficial effects of an ACE inhibitor on structural remodeling. First, we examined the effects of the ACE inhibitor temocapril and the angiotensin II AT 1 subtype receptor antagonist CS-866 on the structural remodeling induced by administering L-NAME for 8 weeks. Temocapril and CS-866 were equally effective in preventing remodeling. Second, we examined whether the effect of temocapril on the remodeling induced by L-NAME was reduced by the bradykinin receptor antagonist HOE140. The latter drug did not alter the beneficial effect of temocapril on remodeling. In conclusion, although species differences must be considered to apply our conclusion to clinical conditions, the present results suggest that the inhibition of angiotensin II activity, mediated via the AT 1 receptors, is responsible for the beneficial effects of an ACE inhibitor in our animal model of coronary vascular and myocardial remodeling induced by the long-term inhibition of NO synthesis.

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          Most cited references18

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          The L-arginine-nitric oxide pathway.

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            Chronic inhibition of nitric oxide synthesis. A new model of arterial hypertension.

            Recent studies have indicated that acute inhibition of nitric oxide biosynthesis in the rat promotes arterial hypertension and renal vasoconstriction. We evaluated the renal and systemic effects of 4-6 weeks of nitric oxide blockade in Munich-Wistar rats receiving the nitric oxide inhibitor nitro-L-arginine orally. Age-matched untreated rats were used as controls. In an additional seven rats, nitric oxide blockade was carried out in conjunction with oral administration of the novel angiotensin II antagonist losartan potassium. Tail-cuff pressure rose progressively in nitro-L-arginine-treated rats, reaching 164 +/- 6 mm Hg at 4-6 weeks, compared with 108 +/- 3 mm Hg in controls. In rats concomitantly receiving losartan, tail-cuff pressure reached 125 +/- 6 mm Hg, still elevated compared with rats receiving losartan alone (98 +/- 3 mm Hg). Nitro-L-arginine-treated rats presented marked renal vasoconstriction and hypoperfusion, as well as a 30% fall in glomerular filtration rate and a 39% increase in filtration fraction. Treatment with Losartan normalized glomerular filtration rate, but not filtration fraction or renal vascular resistance. Plasma renin activity was elevated after nitro-L-arginine treatment. Renal histological examination revealed widespread arteriolar narrowing, focal arteriolar obliteration, and segmental fibrinoid necrosis in the glomeruli. In a separate group of rats, nitro-L-arginine administered for 1 week induced hypertension that was partially reversed by acute L-arginine, but not D-arginine or L-glycine, infusions. We conclude that chronic nitric oxide blockade may constitute a new model of severe arterial hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)
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              Chronic blockade of nitric oxide synthesis in the rat produces systemic hypertension and glomerular damage.

              Tonic basal release of nitric oxide (NO) by vascular endothelial cells controls blood pressure (BP) in the basal state. In these studies we investigated the effects of chronic inhibition of basal NO synthesis in the rat for a 2-mo period. Significant systemic hypertension developed in chronically NO-blocked rats compared to controls. Marked renal vasoconstriction was also observed with elevations in glomerular blood pressure (PGC) and reductions in the glomerular capillary ultrafiltration coefficient (Kf). Chronically NO-blocked rats also develop proteinuria and glomerular sclerotic injury compared to controls. These studies therefore describe a new model of systemic hypertension with glomerular capillary hypertension and renal disease due to chronic blockade of endogenous NO synthesis. These observations highlight the importance of the endogenous NO system in control of normal vascular tone and suggest that hypertensive states may result from relative NO deficiency.
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                Author and article information

                Journal
                Hypertension
                Hypertension
                Ovid Technologies (Wolters Kluwer Health)
                0194-911X
                1524-4563
                December 1997
                December 1997
                : 30
                : 6
                : 1621-1627
                Affiliations
                [1 ]From the Research Institute of Angiocardiology and Cardiovascular Clinic (M.T., K.E., H.T., M.U., H.S., A.T.) and the First Department of Pathology (K.S.), Kyushu University School of Medicine, Fukuoka, Japan, and the Department of Cardiovascular Medicine (H.O., A.K.), Hokkaido University School of Medicine, Sapporo, Japan.
                Article
                10.1161/01.HYP.30.6.1621
                21d930f7-48d9-4414-a157-7c85c5b8dcec
                © 1997
                History

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