Abstract
Injections of the angiotensin(1-7) [Ang(1-7)] antagonist [d-Ala7]-Ang(1-7) into the nucleus of the solitary tract (NTS) of Sprague-Dawley rats reduce baroreceptor reflex sensitivity (BRS) for control of heart rate by approximately 40%, whereas injections of the angiotensin II (Ang II) type 1 receptor antagonist candesartan increase BRS by 40% when reflex bradycardia is assessed. The enzyme angiotensin-converting enzyme 2 (ACE2) is known to convert Ang II to Ang(1-7). We report that ACE2 activity, as well as ACE and neprilysin activities, are present in plasma membrane fractions of the dorsomedial medulla of Sprague-Dawley rats. Moreover, we show that BRS for reflex bradycardia is attenuated (1.16 +/- 0.29 ms mmHg-1 before versus 0.33 +/- 0.11 ms mmHg-1 after; P < 0.05; n = 8) 30-60 min following injection of the selective ACE2 inhibitor MLN4760 (12 pmol in 120 nl) into the NTS. These findings support the concept that within the NTS, local synthesis of Ang(1-7) from Ang II is required for normal sensitivity for the baroreflex control of heart rate in response to increases in arterial pressure.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Angiotensin-Converting Enzyme 2
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Angiotensin-Converting Enzyme Inhibitors / administration & dosage
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Angiotensin-Converting Enzyme Inhibitors / pharmacology*
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Animals
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Baroreflex / drug effects*
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Blood Pressure / drug effects
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Blood Pressure / physiology
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Heart Rate / drug effects*
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Imidazoles / administration & dosage
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Imidazoles / pharmacology*
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Leucine / administration & dosage
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Leucine / analogs & derivatives*
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Leucine / pharmacology
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Male
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Medulla Oblongata / enzymology
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Medulla Oblongata / metabolism
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Membranes / drug effects
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Membranes / metabolism
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Neprilysin / metabolism
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Peptidyl-Dipeptidase A / metabolism*
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Phenylephrine / pharmacology
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RNA, Messenger / biosynthesis
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RNA, Messenger / genetics
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Rats
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Rats, Sprague-Dawley
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Solitary Nucleus / physiology*
Substances
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2-(1-carboxy-2-(3-(3,5-dichlorobenzyl)-3H-imidazol-4-yl)ethylamino)-4-methylpentanoic acid
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Angiotensin-Converting Enzyme Inhibitors
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Imidazoles
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RNA, Messenger
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Phenylephrine
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Peptidyl-Dipeptidase A
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Ace2 protein, rat
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Angiotensin-Converting Enzyme 2
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Neprilysin
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Leucine