Coronary vasoconstrictor influence of angiotensin II is reduced in remodeled myocardium after myocardial infarction

Am J Physiol Heart Circ Physiol. 2006 Nov;291(5):H2082-9. doi: 10.1152/ajpheart.00861.2005. Epub 2006 Jun 23.

Abstract

The renin-angiotensin system plays an important role in cardiovascular homeostasis by contributing to the regulation of blood volume, blood pressure, and vascular tone. Because AT(1) receptors have been described in the coronary microcirculation, we investigated whether ANG II contributes to the regulation of coronary vascular tone and whether its contribution is altered during exercise. Since the renin-angiotensin system is activated after myocardial infarction, resulting in an increase in circulating ANG II, we also investigated whether the contribution of ANG II to the regulation of vasomotor tone is altered after infarction. Twenty-six chronically instrumented swine were studied at rest and while running on a treadmill at 1-4 km/h. In 13 swine, myocardial infarction was induced by ligation of the left circumflex coronary artery. Blockade of AT(1) receptors (irbesartan, 1 mg/kg iv) had no effect on myocardial O(2) consumption but resulted in an increase in coronary venous O(2) tension and saturation both at rest and during exercise, reflecting coronary vasodilation. Despite increased plasma levels of ANG II after infarction and maintained coronary arteriolar AT(1) receptor levels, the vasodilation evoked by irbesartan was significantly reduced both at rest and during exercise. In conclusion, despite elevated plasma levels, the vasoconstrictor influence of ANG II on the coronary circulation in vivo is reduced after myocardial infarction. This reduction in ANG II-induced coronary vasoconstriction may serve to maintain perfusion of the remodeled myocardium.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angiotensin II / blood
  • Angiotensin II / pharmacology*
  • Angiotensin II Type 1 Receptor Blockers / metabolism
  • Animals
  • Biphenyl Compounds / pharmacology
  • Body Weight
  • Coronary Circulation / physiology
  • Exercise Test
  • Female
  • Irbesartan
  • Male
  • Myocardial Infarction / etiology
  • Myocardial Infarction / metabolism*
  • Myocardial Infarction / physiopathology*
  • Myocardium / pathology*
  • Norepinephrine / blood
  • Organ Size
  • Oxygen / metabolism
  • Physical Conditioning, Animal
  • Sus scrofa
  • Tetrazoles / pharmacology
  • Time Factors
  • Vasoconstriction / drug effects
  • Vasoconstriction / physiology
  • Vasoconstrictor Agents / pharmacology*
  • Vasomotor System / drug effects
  • Vasomotor System / physiology

Substances

  • Angiotensin II Type 1 Receptor Blockers
  • Biphenyl Compounds
  • Tetrazoles
  • Vasoconstrictor Agents
  • Angiotensin II
  • Irbesartan
  • Oxygen
  • Norepinephrine