The angiotensin II type 2 receptor and improved adjacent region function post-MI

J Cardiovasc Magn Reson. 2005;7(2):459-64. doi: 10.1081/jcmr-200053461.

Abstract

Angiotensin II type 2 receptor (AT2-R) overexpression in the mouse heart preserves left ventricular (LV) size and global LV function during post-MI remodeling. We hypothesized that CMR tagging would localize regional improvements in myocardial function during post-MI remodeling in AT2-R cardiac overexpressed transgenic mice (TG), which could explain the preservation of global LV function post-MI. Six male wild-type (WT) C57BL/6 mice and 10 TG mice were studied by CMR at baseline (day 0) and days 1, 7, and 28 post-MI. MI was induced by 1 hour occlusion of the LAD followed by reperfusion. On day 1 post-MI, gadolinium-DTPA was injected to assess infarct size. LV size and function was assessed by cine CMR. Mean % circumferential shortening (%CS) was calculated within infarcted, adjacent, and remote regions at each time point in WT and TG mice. Quantitative interstitial collagen and mean myocyte cross-sectional area was measured postmortem at day 28 post-MI. LV end-systolic volume was lower and ejection fraction higher at baseline in the TG group and these differences were maintained post-MI. Within infarcted and remote zones, although %CS was higher in TG mice at day 0, there was no difference by day 28 between groups. Within adjacent regions, while there was no difference at day 0 or 1 in TG vs. WT, %CS was significantly higher in TG mice by day 7, and these changes persisted out to day 28 post-MI. Regional interstitial collagen and myocyte size were similar between groups. Thus, myocardial tagging can detect regional differences in contractile function post-MI in TG mice, and AT2-R overexpression is associated with improved contractile function in adjacent noninfarcted myocardium.

Publication types

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

MeSH terms

  • Angiotensin II / physiology*
  • Animals
  • Collagen / analysis
  • Contrast Media
  • Disease Models, Animal
  • Gadolinium DTPA
  • Heart Ventricles / pathology
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging, Cine*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Myocardial Contraction / physiology
  • Myocardial Infarction / pathology*
  • Myocardial Infarction / physiopathology
  • Myocytes, Cardiac / pathology
  • Receptor, Angiotensin, Type 2 / physiology*
  • Stroke Volume / physiology
  • Systole / physiology
  • Ventricular Dysfunction, Left / pathology
  • Ventricular Dysfunction, Left / physiopathology
  • Ventricular Remodeling / physiology*

Substances

  • Contrast Media
  • Receptor, Angiotensin, Type 2
  • Angiotensin II
  • Collagen
  • Gadolinium DTPA