Calcium Competition with magnesium

Magnesium sulfate, applied intravenously is often used as tocolytic. The mechanism of action is not completely clear but might involve a competition with calcium on the cellular level. Precautions in the sense of magnesium plasma level monitoring must be taken in patients with renal insufficiency since this divalent kation is eliminated by the kidneys. Relatively high plasma concentrations are necessary to achieve a sufficient tocolysis. The relatively frequent side effects are respiratory depression, depressed reflexes, headaches, palpitation and skin flushing in the mother and muscle relaxation and, rarely, CNS depression in the fetus. 

Vanadate, dioxybis(oxamato)-bond-length ratios, 1,57 Vanadate, heptacyano-potassium salt structure, I, 72 Vanadate, hexafluoro-dipotassium salt history, I, 21 potassium salt history, 1,21 tripotassium salt history, 1,21 Vanadate, pentachloro-stereochemistry, 1,40 Vanadate, pentafluorooxy-stereochemistry, I, 50 Vanadates biochemistry, 3,456 calcium/magnesium ATPase inhibition, 6, 567 competition with phosphates physiology, 6,665 protonation, 3,1026 sodium pump, 6, 557 in uranium purification from ore, 6, 899 Vanadates, hexafluoro-, 3. 482,531 Vanadates, oxoperoxo-, 3,501 Vanadates, pentacarbonyl-, 3, 457 Vanadium biology, 6,665 determination, 1. 548 extraction... 

Yermiyahu, U., Nir, S., Ben-Hayyim, G., Kafkafi, U., 1994. Quantitative competition of calcium with sodium or magnesium for sorption sites on plasma membrane vesicles of melon (Cucumis melo L.) root cells. J. Membrane Biol. 138, 55-63. 

Reaction 18.3.1) may produce a calcium deficiency in soil. Acid soils may still contain an appreciable level of calcium which, because of competition by hydrogen ion, is not available to plants. Treatment of acid soil to restore the pH to nearneutrality generally remedies the ealcium deficiency. In alkaline soils, the presence of high levels of sodium, magnesium, and potassium sometimes produees calcium deficiency because these ions compete with calcium for availability to plants. 

The ability of SP to stimulate histamine release from isolated rat peritoneal mast cells is now well demonstrated [31, 97-101], The release is rapid (< 1 min), non-cytotoxic, dependent on a supply of Ca and metabolic energy, and independent of cell-bound IgE [99]. Moreover, as with other peptides, its secretory effect on the mast cell is affected by moderate levels of extracellular cations. For example, the addition of Ca to the bathing medium after the addition of SP increased the secretory response of the cells, while adding calcium (0.1-1 mM), magnesium (1-10 mM) or cobalt (0.01-1 mM) to the cell suspension before SP inhibited histamine release, suggesting the possibility of cation competition for SP binding [99]. 

Compounds that have been proposed to react by this mechanism include barium titanate, calcium titanate, calcium carbonate, strontium titanate and magnesium oxides[8,9,10]. All these basic compounds should theoretically react with vanadic acid and bind it in the trap and have proved effective in laboratory evaluations. However, sulfur competition negatively affects the performance of these traps in commercial units[8,l 1],... 

The catabolites of phytase activity in wheat are myo-inositol, phosphate, and the macroelements potassium, magnesium and calcium. Myo-inositol phosphate ester intermediates with fewer than six phosphate groups do not accumulate within the grain during hydrolysis of the phytin molecule [94], which is indicative of its rapid and complete breakdown by phytases. Movement of the catabolites from the aleurone layer and their redistribution into the developing seedling appears to be by simple diffusion through the endosperm, without any apparent competition for uptake by the scutellum. 

The early period of research into the toxicity of cadmium for animals did not lead to conclusive evidence for a single, ubiquitous, high affinity, and dedicated component that would allow Cd " to cross biological membranes and to obtain indiscriminate access to any location. However, it was soon realized that many ionic channels do interact with Cd ". Numerous electrophysiological studies described the inhibition of potassium, sodium, magnesium, or calcium fluxes by high concentrations of cadmium salts (reviewed in [47]), in neuronal cells in particular. Of note, such inhibitory effects induced by Cd " may not result from simple competition between the physiological cations and cadmium at the sites of transport. Indeed, many... 

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