High-salt diet inhibits expression of angiotensin type 2 receptor in resistance arteries

Hypertension. 2005 May;45(5):853-9. doi: 10.1161/01.HYP.0000161990.98383.ad. Epub 2005 Apr 4.

Abstract

Recent studies suggested that type 2 angiotensin receptor (AT2R) could contribute to regulation of blood pressure and/or vascular remodeling. A key question relates to the effects of potential modulators of vascular AT2R expression. In the present work, we evaluated if high salt intake (70 mmol/L NaCl in drinking water) could modulate rat mesenteric artery AT2R function and expression. Angiotensin II dose-response curves were studied in rat perfused pressurized small-diameter arteries in the presence of losartan (AT1R antagonist). Arteries were precontracted with phenylephrine, yielding approximately 30% decrease in resting diameter. AT2R activation by angiotensin-induced dose-dependent relaxation of precontracted arteries (60.1+/-9.1% of phenylephrine-induced contraction, P<0.05). In contrast, AT2R-dependent relaxation was not observed in arteries obtained from rats on high-salt diet. Semi-quantitative reverse-transcription polymerase chain reaction experiments demonstrated reduced amount of AT2R mRNA in arteries of rats on high-salt diet (65.5+/-7.5% of control levels, P<0.05). Western blot studies demonstrated decreased AT2R in mesenteric artery protein fractions of high-salt diet rats (60.0+/-18.0 of control levels, P<0.05). In a second set of experiments, adrenalectomy (4 days) blunted AT2R-mediated vasorelaxation and decreased AT2R mRNA (72.0+/-11.0% of control levels, P<0.05). AT2R abundance in protein fractions of mesenteric arteries of ADX rats was also diminished (64.0+/-13% of control levels, P<0.05). Both, AT2R mRNA and protein downregulation were prevented by mineralocorticoid replacement therapy. Finally, physiological concentrations of aldosterone caused a dose-dependent increase in AT2R mRNA of small diameter mesenteric artery explants. The results are consistent with aldosterone-mediated upregulation AT2R.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenalectomy
  • Aldosterone / blood
  • Aldosterone / pharmacology
  • Angiotensin II Type 2 Receptor Blockers*
  • Animals
  • Blood Pressure / drug effects
  • Desoxycorticosterone / pharmacology
  • Dose-Response Relationship, Drug
  • Electrolytes / blood
  • In Vitro Techniques
  • Male
  • Mesenteric Arteries / drug effects
  • Mesenteric Arteries / metabolism
  • Mesenteric Arteries / physiology*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Angiotensin, Type 1 / metabolism
  • Receptor, Angiotensin, Type 2 / drug effects
  • Receptor, Angiotensin, Type 2 / genetics
  • Receptor, Angiotensin, Type 2 / metabolism
  • Sodium Chloride, Dietary / administration & dosage*
  • Sodium Chloride, Dietary / pharmacology
  • Vascular Resistance*
  • Vasodilation / drug effects
  • Vasodilation / physiology

Substances

  • Angiotensin II Type 2 Receptor Blockers
  • Electrolytes
  • RNA, Messenger
  • Receptor, Angiotensin, Type 1
  • Receptor, Angiotensin, Type 2
  • Sodium Chloride, Dietary
  • Desoxycorticosterone
  • Aldosterone