title: Regional variation in aortic AT1b receptor mRNA abundance is associated with contractility but unrelated to atherosclerosis and aortic aneurysms.
abstract: BACKGROUND
  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. Although AT1a receptors have been studied comprehensively, roles of AT1b receptors in the aorta have not been defined.
  
  
  RESULTS
  We 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
  Regional abundance of AT1b receptor mRNA coincided with AngII-induced regional contractility, but it was not associated with AngII-induced aortic pathologies.
authors.affiliation: Saha Cardiovascular Research Center, University of Kentucky, Lexington, United States of America.
authors.forename: Aruna
authors.initials: A
authors.lastname: Poduri
authors.forename: A Phillip
authors.initials: AP
authors.lastname: Owens
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Howatt
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Moorleghen
authors.forename: Anju
authors.initials: A
authors.lastname: Balakrishnan
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Cassis
authors.forename: Alan
authors.initials: A
authors.lastname: Daugherty
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001014:Aortic Aneurysm / Q000235:genetics* / Q000378:metabolism; D062186:Arterial Pressure / Q000187:drug effects / Q000235:genetics; D050197:Atherosclerosis / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II