Romanian Society of Pharmaceutical Sciences

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EXTRACELLULAR MG2+ LEVEL AFFECTS THE MAJOR MECHANISM OF ENDOTHELIUM-DEPENDENT RELAXATION IN RESISTANCE ARTERIES

MIHAI CONSTANTIN, DRAGOMIR NICOLAE ŞERBAN *, CĂTĂLIN PRICOP, BOGDAN HUZUM, IONELA LĂCRĂMIOARA ŞERBAN

“Grigore T. Popa” University of Medicine and Pharmacy, 16 Universităţii Street, 700115, Iași, Romania

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Mg2+ affects vascular smooth muscle contraction by direct and endothelium-dependent pathways. The major mechanism of endothelium-dependent relaxation (EDR) in resistance arteries is independent of nitric oxide synthase and cyclooxygenase and mediated by Ca2+-activated K+ channels (sK and iK). We tested the effect of modified extracellular Mg2+ (Mge) concentration upon this mechanism, in isolated small mesenteric arteries from rat. EDR was induced by carbachol 10-8 - 10-4 M, in rings contracted by phenylephrine 10-5 M, in the presence of N(G)-Nitro-L-arginine methyl ester (L-NAME) 10-4 M and indomethacin 10-5 M, with [Mge] kept at 2, 1.2, or 0.8 mM. This EDR is enhanced by high [Mge] and reduced by low [Mge], vs. the one in regular [Mge] of 1.2 mM (n = 6; p < 0.01). Mge similarly modulates relaxation induced by SKA-31 (sK/iK activator). These new Mge actions do not involve known Mg2+ effects on sK/iK and may be relevant in Mg therapy.