AT1 receptor antagonism attenuates target organ effects of salt excess in SHRs without affecting pressure

Am J Physiol Heart Circ Physiol. 2008 Feb;294(2):H853-8. doi: 10.1152/ajpheart.00737.2007. Epub 2007 Nov 30.

Abstract

Our recent studies have demonstrated that salt excess in the spontaneously hypertensive rat (SHR) produces a modestly increased arterial pressure while promoting marked myocardial fibrosis and structural damage associated with altered coronary hemodynamics and ventricular function. The present study was designed to determine the efficacy of an angiotensin II type 1 (AT(1)) receptor blocker (ARB) in the prevention of pressure increase and development of target organ damage from high dietary salt intake. Eight-week-old SHRs were given an 8% salt diet for 8 wk; their age- and gender-matched controls received standard chow. Some of the salt-loaded rats were treated concomitantly with ARB (candesartan; 10 mg kg(-1) day(-1)). The ARB failed to reduce the salt-induced rise in pressure, whereas it significantly attenuated left ventricular (LV) remodeling (mass and wall thicknesses), myocardial fibrosis (hydroxyproline concentration and collagen volume fraction), and the development of LV diastolic dysfunction, as shown by longer isovolumic relaxation time, decreased ratio of peak velocity of early to late diastolic waves, and slower LV relaxation (minimum first derivative of pressure over time/maximal LV pressure). Without affecting the increased pulse pressure by high salt intake, the ARB prevented the salt-induced deterioration of coronary and renal hemodynamics but not the arterial stiffening or hypertrophy (pulse wave velocity and aortic mass index). Additionally, candesartan prevented the salt-induced increase in kidney mass index and proteinuria. In conclusion, the ARB given concomitantly with dietary salt excess ameliorated salt-related structural and functional cardiac and renal abnormalities in SHRs without reducing arterial pressure. These data clearly demonstrated that angiotensin II (via AT(1) receptors), at least in part, participated importantly in the pressure-independent effects of salt excess on target organ damage of hypertension.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin II Type 1 Receptor Blockers / pharmacology*
  • Animals
  • Aorta, Thoracic / diagnostic imaging
  • Aorta, Thoracic / pathology
  • Aorta, Thoracic / physiology
  • Blood Pressure / drug effects*
  • Body Weight / drug effects
  • Body Weight / physiology
  • Coronary Circulation / drug effects
  • Fibrillar Collagens / metabolism
  • Hydroxyproline / metabolism
  • Hypertrophy, Left Ventricular / diagnostic imaging
  • Hypertrophy, Left Ventricular / physiopathology
  • Kidney / anatomy & histology
  • Kidney / drug effects
  • Male
  • Proteinuria / prevention & control
  • Rats
  • Rats, Inbred SHR
  • Renal Circulation / drug effects
  • Sodium Chloride, Dietary / administration & dosage
  • Sodium Chloride, Dietary / adverse effects*
  • Ultrasonography
  • Vascular Resistance / drug effects

Substances

  • Angiotensin II Type 1 Receptor Blockers
  • Fibrillar Collagens
  • Sodium Chloride, Dietary
  • Hydroxyproline