Angiotensin II-induced vascular dysfunction is mediated by the AT1A receptor in mice.
Many of the actions of angiotensin II (Ang II) are mediated by angiotensin type 1 receptors (AT1), of which there are 2 pharmacologically indistinguishable subtypes (AT1A and AT1B). The purpose of this study was to evaluate the effect of an AT1A homozygous deletion (AT1A-/-) on vascular reactivity. AT1A-/- mice and control littermates (AT1A+/+) were infused with vehicle (saline) or Ang II (1000 ng x kg(-1) x min(-1)) for 7 days by osmotic pumps. Systolic pressure was increased in AT1A+/+ mice (Delta45+/-8 mm Hg, P<0.0001) but unchanged in AT1A-/- mice (Delta5+/-3 mm Hg, P>0.13) on day 7. The carotid artery response to the vasodilators acetylcholine (ACh), nitroprusside, and papaverine and to the vasoconstrictors phenylephrine, U46619, 5-hydroxytryptamine (5-HT), and KCl were not different between vehicle-infused AT1A+/+ and AT1A-/- animals. Carotid relaxation to ACh was impaired and contraction to 5-HT was increased in Ang II-infused AT1A+/+ mice. Ang II did not affect carotid responses in AT1A-/- mice. Superoxide, measured by lucigenin (5 micromol/L), and hydroethidine staining were not different between AT1A+/+ and AT1A-/- mice after vehicle or Ang II infusion, suggesting that it was not contributing to the altered ACh and 5-HT responses. The Rho-kinase inhibitor Y-27632 (1 micromol/L) attenuated the 5-HT response in both vehicle- and Ang II-infused AT1A+/+ mice. Moreover, concentration-dependent relaxation to Y-27632 and RhoA protein expression were not different in vehicle- or Ang II-infused AT1A+/+. These data demonstrate that the AT1A receptor is required for Ang II-induced changes in carotid artery function.
Department of Internal Medicine, Cardiovascular Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City 52242, USA. ryanm@physiology.uiowa.edu
Michael J
MJ
Ryan
Sean P
SP
Didion
Satya
S
Mathur
Frank M
FM
Faraci
Curt D
CD
Sigmund
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000804:Angiotensin II / Q000008:administration & dosage / Q000633:toxicity*; D000818:Animals; D001011:Aorta / Q000378:metabolism; D002339:Carotid Arteries / Q000187:drug effects; D015918:Infusion Pumps, Implantable; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000502:physiology; D009599:Nitroprusside / Q000494:pharmacology; D010208:Papaverine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D044140:Receptor, Angiotensin, Type 1 / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D044139:Receptor, Angiotensin, Type 2 / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D012701:Serotonin / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D020742:rhoA GTP-Binding Protein
D000577:Amides; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D013481:Superoxides; D000804:Angiotensin II; C108830:Y 27632; D009599:Nitroprusside; D010656:Phenylephrine; D009569:Nitric Oxide; D012701:Serotonin; D011189:Potassium Chloride; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D010208:Papaverine; D020742:rhoA GTP-Binding Protein; D000109:Acetylcholine