Chronic Blockade of Nitric Oxide Synthesis Elevates Plasma Levels of Catecholamines and Their Metabolites at Rest and During Stress in Rats |
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Authors: | Kvetňanský Richard Pacák Karel Tokarev Dmitrij Jeloková Jana Ježová Daniela Rusnák Milan |
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Affiliation: | (1) Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlarska 3, 833 06 Bratislava, Slovak Republic;(2) Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland, 20892;(3) Washington Hospital Center, Department of Medicine, Washington, D.C. Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland, 20892 |
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Abstract: | Formation of nitric oxide, an endothelium-derived relaxing factor, can be inhibited by administration of N-nitro-L-arginine methylesther (L-NAME). In the present study, the activity of the sympathoadrenal system in rats with blood pressure (BP) elevation induced by L-NAME was investigated. L-NAME was administered in a dose of 50 mg/kg, i.p. every 12 h for 4 days. Blood samples were collected via chronically inserted arterial catheters in conscious, freely moving rats at rest and during immobilization stress. Plasma epinephrine (EPI), norepinephrine (NE), and dopamine (DA), as well as catecholamine metabolites dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) were measured by HPLC method. In L-NAME treated animals, which showed a significant increase in BP, plasma EPI levels were markedly elevated both before and during stress. Plasma NE levels were not significantly increased, however, DHPG levels, which indicate NE turnover and reuptake, were highly elevated. Plasma DA levels were not changed after L-NAME administration but DA metabolite DOPAC showed a significant elevation both under basal conditions and during stress. Thus, the present results indicate that the prolonged blockade of nitric oxide synthesis that causes arterial hypertension is associated with an activation of the sympathoadrenal system. |
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Keywords: | Norepinephrine epinephrine dopamine dihydroxyphenylglycol (DHPG) -lacetic acid (DOPAC) stress nitric oxide synthase inhibition nitro-L-arginine methylesther (L-NAME) |
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