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Submitted on March 26, 2002
From Franz-Volhard Clinical Research Center and HELIOS Klinikum Berlin (J.J., J.T., C.S., M.S., G.F., A.M.S., F.C.L.) and the Department of Neurology (A.L., G.A.), Medical Faculty of the Charité, Humboldt-University, Berlin, Germany; Autonomic Dysfunction Service, Vanderbilt University, Nashville, Tenn (A.D.); and the Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Md (D.S.G.). * To whom correspondence should be addressed. E-mail: jordan{at}fvk-berlin.de.
BackgroundWhether catechol-O-methyltransferase (COMT), the enzyme that metabolizes extraneuronal norepinephrine, contributes to blood pressure regulation in humans is unknown. Methods and ResultsWe studied incremental doses of the COMT inhibitor entacapone, the sympathetic stimulant yohimbine, and placebo in 7 patients with multiple system atrophy (Shy Drager syndrome). We selected these unique subjects because norepinephrine exerts an exaggerated increase in blood pressure in these patients. Autonomic regulation was characterized with intravenous phenylephrine, nitroprusside, and trimethaphan. Patients were extremely hypersensitive to phenylephrine and nitroprusside. Trimethaphan elicited a profound depressor response. Phenylephrine sensitivity increased only slightly during ganglionic blockade. Entacapone increased systolic blood pressure dose-dependently; however, the pressor response to yohimbine was ConclusionsCOMT inhibition elicits a moderate, dose-dependent pressor response in the setting of severely impaired baroreflex buffering. Patients with multiple system atrophy allow for the characterization of subtle manipulations of norepinephrine turnover and blood pressure regulation in small numbers of subjects.
Revised on May 9, 2002
Accepted on May 9, 2002
Catechol-O-Methyltransferase and Blood Pressure in Humans
Jens Jordan MD*,
3.5 times greater than the maximal response to entacapone.
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