Influence of endothelium on Mg(2+)-induced relaxation in noradrenaline-contracted aorta from DOCA-salt hypertensive rat

Eur J Pharmacol. 1994 Jun 13;258(3):167-72. doi: 10.1016/0014-2999(94)90477-4.

Abstract

The aim of this study was to examine the influence of vascular endothelium on the relaxation induced by increased extracellular Mg2+ concentrations on isolated and noradrenaline-precontracted aorta from deoxycorticosterone acetate-salt (DOCA-salt) hypertensive and normotensive rats. In Mg(2+)-free physiologic salt solution (PSS), addition of Mg2+ (0.1-6.0 nM) caused concentration-dependent relaxation of noradrenaline-precontracted aorta with intact or disrupted endothelium. Mg(2+)-induced relaxation in intact aorta, however, was less in DOCA-salt hypertensive rats than in normotensive rats. When endothelium was disrupted, Mg(2+)-induced relaxation was depressed in aorta from both DOCA-salt hypertensive and normotensive rats. The same observations were made in presence of N-nitro-L-arginine methyl ester (L-NAME), an inhibitor of endothelium-derived relaxing factor nitric oxide (EDRF/NO) biosynthesis. Mg(2+)-induced relaxation following contraction with noradrenaline was significantly less in intact aorta treated with L-NAME from DOCA-salt hypertensive rats than in intact aorta from normotensive rats. Indomethacin did not affect Mg(2+)-induced relaxation in intact aorta from normotensive rats whereas indomethacin significantly increased it in DOCA-salt hypertensive rats. It is concluded that (1) Mg(2+)-induced relaxation can be mediated by endothelium-dependent mechanisms implicating EDRF/NO; (2) the influence of EDRF/NO is more pronounced on the impaired Mg(2+)-induced relaxation of aorta from DOCA-salt hypertensive rats; (3) Mg(2+)-induced relaxation seems masked by vasoconstrictor prostaglandin release in DOCA-salt hypertensive rats; (4) these differences between normotensive and hypertensive rats could be related to the impaired endothelial function in aorta from DOCA-salt hypertensive rats.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Arginine / analogs & derivatives
  • Arginine / pharmacology
  • Desoxycorticosterone
  • Endothelium, Vascular / physiology*
  • Hypertension / chemically induced
  • Hypertension / physiopathology*
  • Magnesium / pharmacology*
  • Male
  • Muscle Contraction / drug effects
  • Muscle Relaxation / drug effects
  • Muscle, Smooth, Vascular / drug effects*
  • NG-Nitroarginine Methyl Ester
  • Nitric Oxide / antagonists & inhibitors
  • Norepinephrine / pharmacology*
  • Rats
  • Rats, Sprague-Dawley

Substances

  • Nitric Oxide
  • Desoxycorticosterone
  • Arginine
  • Magnesium
  • NG-Nitroarginine Methyl Ester
  • Norepinephrine