Szabó C, Faragó M, Dóra E, Horváth I, Kovách A G
Experimental Research Department, Semmelweis University Medical School, Budapest, Hungary.
Acta Physiol Hung. 1991;78(1):19-26.
To clarify the effect of extracellular magnesium on the vascular reactivity of feline isolated mesenteric arteries, the effects of slight alterations in the extracellular magnesium concentration on the contractile and endothelium-dependent dilatory responses were investigated in vitro. The contractions, induced by noradrenaline 10(-8)-10(-5) M, were not affected in the mesenteric artery at low extracellular magnesium (0.8 mM versus to the normal, 1.2 mM). High (1.6 and 2.0 mM) magnesium exerted a modest inhibitory effect on the contractile responses. This depression of the contraction was accompanied with a significant shift to the right in the EC50 value for noradrenaline. The endothelium-dependent relaxations induced by acetylcholine 10(-8)-10(-5) M, were inhibited by high (1.6 and 2.0 mM) magnesium. Lowering of the extracellular magnesium concentration to 0.8 mM, however, failed to alter the dilatory potency of acetylcholine. The depression of the dilatory responses was also accompanied with a shift to the right in the EC50 values for acetylcholine. The present results show, that contractions and endothelium-dependent relaxations of the mesenteric artery are modulated by the extracellular magnesium asymmetrically: slight magnesium deficiency does not affect these responses, whereas elevation of the concentration of this ion inhibits both processes. Extracellular magnesium probably affects rather the binding of these contractile and endothelium-dependent dilatory agonists to their receptors than the calcium influx into the endothelial- and smooth muscle cells in this vessel.
为阐明细胞外镁对猫离体肠系膜动脉血管反应性的影响，体外研究了细胞外镁浓度的轻微改变对收缩反应和内皮依赖性舒张反应的影响。由10(-8)-10(-5)M去甲肾上腺素诱导的收缩，在低细胞外镁（0.8mM，与正常的1.2mM相比）条件下，肠系膜动脉的收缩不受影响。高浓度（1.6和2.0mM）镁对收缩反应有适度的抑制作用。这种收缩的抑制伴随着去甲肾上腺素EC50值显著右移。由10(-8)-10(-5)M乙酰胆碱诱导的内皮依赖性舒张，受到高浓度（1.6和2.0mM）镁的抑制。然而，将细胞外镁浓度降至0.8mM，未能改变乙酰胆碱的舒张效力。舒张反应的抑制也伴随着乙酰胆碱EC50值右移。目前的结果表明，肠系膜动脉的收缩和内皮依赖性舒张受到细胞外镁的不对称调节：轻微的镁缺乏不影响这些反应，而该离子浓度升高则抑制这两个过程。细胞外镁可能主要影响这些收缩性和内皮依赖性舒张激动剂与其受体的结合，而不是该血管内皮细胞和平滑肌细胞的钙内流。
