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(Hypertension. 2005;45:845.)
© 2005 American Heart Association, Inc.

Editorial Commentaries

Microvascular Effects of Aldosterone and Angiotensin Type 2 Receptors

Thomas L. Pallone

From the Division of Nephrology, Departments of Medicine and Physiology, University of Maryland at Baltimore.

Correspondence to Thomas L. Pallone, MD, Division of Nephrology, N3W143, 22 S Greene St, University of Maryland Medical System, Baltimore, MD 21201. E-mail tpallone@medicine.umaryland.edu

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

In the current issue of Hypertension, Gonzalez et al describe the modulation of mesenteric vascular angiotensin type 2 receptor (AT2R) expression by aldosterone.¹ The principal findings are as follows: (1) AT2R activation dilates phenylephrine preconstricted mesenteric arterioles; (2) 4 days of oral salt loading eliminates AT2R-mediated dilation and reduces expression of AT2R mRNA and protein; (3) an adrenal hormone is implicated because the effects of salt loading are mimicked by adrenalectomy; (4) of the candidate adrenal hormones, aldosterone is identified because mineralocorticoid replacement prevents the effects of adrenalectomy; and (5) aldosterone upregulates AT2R expression in explanted mesenteric arterioles. These well designed series of experiments strongly support a role for aldosterone to stimulate expression of AT2R and adds to the growing repertoire of roles that aldosterone plays in vasculature physiology.

The AT2R-mediated vasodilation observed by Gonzalez et al¹ elegantly reproduces similar effects reported in the mesentery and other vascular preparations.^2–5 AT2R induced vasodilation of mesenteric arterioles appears as endothelium-dependent,⁶ acts through kinin and nitric oxide (NO) generation,⁷ and involves myocyte hyperpolarization through stimulation of large-conductance Ca²⁺-dependent potassium channels.⁸ Such AT2R-mediated reduction of vascular resistance generalizes beyond the mesenteric vascular bed. Systemic AT2R activation through infusion of angiotensin II plus AT1 receptor blockers lowers blood pressure⁹ and AT2-null mice have mild hypertension with an exaggerated blood pressure response to deoxycorticosterone acetate plus salt.^10,11 Carotid arteries,¹² coronary arterioles,¹³ renal afferent arterioles,^14–16 and descending vasa recta¹⁷ are dilated by AT2R activation. The participation of bradykinin B2 receptor activation and NO generation in . . . [Full Text of this Article]

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High-Salt Diet Inhibits Expression of Angiotensin Type 2 Receptor in Resistance Arteries

Magdalena Gonzalez, Lorena Lobos, Felipe Castillo, Lorna Galleguillos, Nandy C. Lopez, and Luis Michea
Hypertension 2005 45: 853-859. [Abstract] [Full Text] [PDF]