title: Influence of endothelium in the in vitro vasorelaxant effect of magnesium on aortic basal tension in DOCA-salt hypertensive rat.
abstract: The objective of this study was to examine the influence of the endothelium on the extracellular magnesium induced relaxation of basal tension in isolated aortas from both mineralocorticoid-salt (DOCA-salt) hypertensive and control normotensive Sprague Dawley male rats. After incubation in magnesium-free physiological salt solution (PSS) (O mM magnesium), the increase of extracellular magnesium (1.2; 4.8 mM magnesium) caused a decrease in aortic tone which was significantly greater when endothelium was disrupted. Magnesium-induced relaxation was also more pronounced when endothelial NO production was blocked by 10(-4) M N omega-nitro-L arginine methyl ester (L-NAME). It is suggested that the vasorelaxation induced by extracellular magnesium is linked to the level of aortic basal tension developed in magnesium-free PSS. The endothelium does not seem to be directly implicated in magnesium-induced vasorelaxation in aortas from normotensive rats. However, in DOCA-salt hypertensive rats, the magnesium-induced relaxation of basal tension was less in the intact aorta (though not when the endothelium was disrupted) when the cyclo-oxygenase pathway was blocked by 10(-6) M indomethacin. These data therefore suggest that extracellular magnesium can promote relaxation by endothelium-dependent and cyclo-oxygenase-dependent mechanisms such as the production of relaxing prostacyclin in isolated aorta from DOCA-salt hypertensive rats.
authors.affiliation: Laboratoire de Physiologie Pharmacie, UFR de Médecine et Pharmacie, Besançon, France.
authors.forename: P
authors.initials: P
authors.lastname: Laurant
authors.forename: A
authors.initials: A
authors.lastname: Berthelot
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D003900:Desoxycorticosterone; D004730:Endothelium, Vascular / Q000502:physiology*; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D003900:Desoxycorticosterone; D001120:Arginine; D008274:Magnesium; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine; D007213:Indomethacin