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(Circulation. 2005;111:956-957.)
© 2005 American Heart Association, Inc.

Editorial

Influence of Changes of Blood Pressure on Vascular Angiotensin II Receptor Subtype Expression

Anthony M. Heagerty, MD, FRCP, FMedSci

From the Cardiovascular Research Division, Department of Medicine, Manchester Royal Infirmary, Manchester, UK.

Correspondence to Dr Anthony M. Heagerty, Cardiovascular Research Division, Dept of Medicine, Manchester Royal Infirmary, Oxford Rd, Manchester M13 9WL, UK. E-mail tony.heagerty@man.ac.uk

Key Words: Editorials • angiotensin • receptors • blood pressure • pharmacology

An extract of the first 250 words of the full text is provided, because this article has no abstract.

The evolving complexity associated with the renin-angiotensin cascade has been the focus of increasingly sophisticated pharmacological experimentation. The identification of at least 2 angiotensin II (Ang II) receptor subtypes led to functional subclassification of their activity. Activation of the type 1 (AT₁) receptor is associated with the vasopressive and aldosterone-secreting effects of Ang II. Mice that lack the gene that encodes the AT₂ receptor demonstrate normal development but an impaired drinking response to water deprivation and a reduction in spontaneous movements.¹ Basal blood pressure is higher, and sensitivity to the pressor actions of exogenously delivered Ang II is increased.^1,2 Differences in diastolic blood pressure persist even when AT₁ receptors are blocked by losartan, indicating that this effect is independent of AT₁. The greater pressor response to Ang II requires AT₁ receptor activation and therefore, normally, AT₂ receptors may serve to limit this.³ As a consequence, the concept of a vasodilator role for this receptor was introduced.

See p 1006

Subsequently, a variety of reports have emerged linking the stimulation of AT₂ with vasodilation in small resistance arteries in normotensive rats. The mechanism invoked usually is associated with nitric oxide (NO) production by endothelial cells and cGMP production by vascular smooth muscle cells. In addition, some studies have demonstrated bradykinin B₂ receptor activation may be involved. What is not in question is the ubiquity of the AT₂ receptor in vascular tissues, with studies localizing them to the endothelium, smooth muscle, and adventitia. A dilator function in circulatory homeostasis seems . . . [Full Text of this Article]

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