Abstract

BackgroundAngiotensin II (AngII), the main bioactive peptide of the renin angiotensin system, exerts most of its biological actions through stimulation of AngII type 1 (AT1) receptors. This receptor is expressed as 2 structurally similar subtypes in rodents, termed AT1a and AT1b. Although AT1a receptors have been studied comprehensively, roles of AT1b receptors in the aorta have not been defined.Methodology/ResultsWe initially compared the regional distribution of AT1b receptor mRNA with AT1a receptor mRNA in the aorta. mRNA abundance of both subtypes increased from the proximal to the distal aorta, with the greatest abundance in the infra-renal region. Corresponding to the high mRNA abundance for both receptors, only aortic rings from the infra-renal aorta contracted in response to AngII stimulation. Despite the presence of both receptor transcripts, deletion of AT1b receptors, but not AT1a receptors, diminished AngII-induced contractility. To determine whether absence of AT1b receptors influenced aortic pathologies, we bred AT1b receptor deficient mice into an LDL receptor deficient background. Mice were fed a diet enriched in saturated fat and infused with AngII (1,000 ng/kg/min). Parameters that could influence development of aortic pathologies, including systolic blood pressure and plasma cholesterol concentrations, were not impacted by AT1b receptor deficiency. Absence of AT1b receptors also had no effect on size of aortic atherosclerotic lesions and aortic aneurysms in both the ascending and abdominal regions.Conclusions/SignificanceRegional abundance of AT1b receptor mRNA coincided with AngII-induced regional contractility, but it was not associated with AngII-induced aortic pathologies.

Highlights

  • Angiotensin II (AngII) is the major effector of the renin angiotensin system that exerts its actions predominantly through stimulation of AngII type 1 (AT1) receptors [1,2,3]

  • The present study examined the role of AT1b receptors in aortic tissues in response to AngII

  • We initially demonstrated the concordance of the regional abundance of AT1b receptor mRNA and the presence of functional AT1b receptors in the aorta as the primary mediator of AngII-induced region-specific contractile response

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Summary

Introduction

Angiotensin II (AngII) is the major effector of the renin angiotensin system that exerts its actions predominantly through stimulation of AT1 receptors [1,2,3] In rodents, this receptor undergoes chromosomal duplication and is expressed as two subtypes, named AngII type 1a (AT1a) and type 1b (AT1b) receptors [4]. Angiotensin II (AngII), the main bioactive peptide of the renin angiotensin system, exerts most of its biological actions through stimulation of AngII type 1 (AT1) receptors. This receptor is expressed as 2 structurally similar subtypes in rodents, termed AT1a and AT1b. AT1a receptors have been studied comprehensively, roles of AT1b receptors in the aorta have not been defined

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