The Effect of Magnesium on the Response of Smooth Muscle to 5‐hydroxytryptamine

Abstract

The responses to 5‐hydroxytryptamine (5‐HT) of rabbit isolated mesenteric artery and vein and longitudinal smooth muscle of guinea‐pig ileum were examined in Krebs solution containing 0, 1.2 or 2.4 mm Mg2+. When the concentration of Mg2+ was raised the spontaneous contractile activity of rabbit mesenteric vein was depressed. The responses to 5‐HT in rabbit mesenteric artery and vein and guinea‐pig ileum were greater in the absence of Mg2+. The initial fast component of 5‐HT‐induced contractions in rabbit mesenteric vein was reduced more consistently than the subsequent slow component by increasing the Mg2+ concentration. Exposure of mesenteric vein to Ca‐free solution containing ethyleneglycoltetra‐acetic acid (EGTA) promptly abolished 5‐HT contraction in normal‐Mg but not in low‐Mg Krebs solution. In mesenteric veins, no difference was observed in either the ‘lanthanum‐resistant’ uptake of 45Ca or total tissue Ca, measured by atomic absorption spectrophotometry, after 60 min exposure to either low‐Mg or normal‐Mg Krebs solution. On the other hand, after 5 min exposure, the ‘lanthanum‐resistant’ uptake of 45Ca was greater in the absence of Mg2+ than in the presence of higher Mg2+ concentrations. It is suggested that Mg2+ depressed the 5‐HT response at least partly by reducing the availability of Ca2+ from a rapidly equilibrating intracellular pool.

Plasma and Membrane Ca²⁺ and Mg²⁺ Concentrations in Normal Pregnancy and in Preeclampsia

“…Recently, in single myocytes from frog ventricle, the site of interaction between Mg 2+ and Ca 2+ was identified as the Ca 2+ inward current that is dependent on phosphorylation by cyclic adenosine monophosphatase [31]. Sec-Kisters/Körner/Louwen/Witteler/Jackisch/ Zidek/Ott/Westermann/Barenbrock/Rahn ond, changes in the extracellular Mg 2+ concentration induced inverse changes in the Ca 2+ content of vascular smooth muscle and in exchangeable Ca 2+ [31][32][33]. These findings suggest competition between Mg 2+ and Ca 2+ for intracellular binding sites as a further mechanism for Mg 2+ -induced vasodilation.…”

Effects of Magnesium on Human Umbilical Arteries: Role of Intracellular Calcium Stores

“…It has been demonstrated that Mg 2+ can produce not only relaxation per se, but is also capable of modulating the vascular reactivity to a large number of substances such as potassium, prostaglandin F 2· , noradrenaline and 5-HT [26]. In a study performed by Turlapaty and Altura [27], it was clearly demonstrated that the calcium movements in the aorta and portal veins of the rat are influenced by extracellular Mg 2+ concentrations.…”

A comparative study of magnesium, flunarizine and amitriptyline in the prophylaxis of migraine

“…Serotonin receptor activity is altered by changes in levels of ionized Mg +2 [31,32] and vasoconstriction induced by serotonin can be effectively blocked by pretreatment with Mg +2 [33]. Experimental Mg +2 deficiency leads to generation and release of substance P [34] which is thought to act on sensory fibers and cause the pain in headache [35].…”