Intracellular magnesium: transport and regulation in epithelial secretory cells

Abstract

ABSTRACT] i from magfura-2-loaded acini and acinar cells and Mg 2+ content in effluent samples from perfused pancreatic segments, respectively, confirm that secretagogues such as acetylcholine (ACh) and cholecystokinin-octapeptide (CCK-8) can evoke marked and significant extrusion of Mg 2+ which is closely associated with the mobilization of intracellular calcium. These effects may be modulated by different mediators including cAMP, Protein Kinase C and nitric oxide/cGMP. This reduction in [Mg 2+ ] i seems to be a prerequisite for optimal generation and maintenance of the calcium signal and subsequently, the secretion of enzymes, since an increase in extracellular Mg

Cell signaling, beyond cytosolic calcium in eukaryotes

“…In excitable cells, [Mg 2+ ] cyt is several hundred times lower than expected if Mg 2+ ions were at electrochemical equilibrium. In squid giant axons and barnacle muscle cells a 2Na + , 2K + , 2Cl À : 1Mg 2+ exchanger is supposedly responsible for transporting Mg 2+ ions across the plasmalemma and for maintaining [Mg 2+ ] cyt at steady-state conditions [117].…”

Does a higher ratio of serum calcium to magnesium increase the risk for postmenopausal breast cancer?

“…Mg plays an essential role in more than 300 biological activities [28]. Within the cell, Mg affects the function of organelles such as sarcoplasmic reticulum, primarily by its ability to alter Ca influx [29,30] or mitochondria by altering their membrane’s permeability to protons, which leads to alterations in the coupling of oxidative phosphorylation and electron transport chains, thus affecting the efficiency of ATP production. A decrease in serum Mg could decrease Mg levels inside the cells, which will lead to a decrease in Mg–ATP levels.…”

Magnesium in Man: Implications for Health and Disease

“…In the pancreatic acini, intracellular Mg 2ϩ antagonizes Ca 2ϩ -activated signaling events and enzyme secretion (573). It is known that ACh and cholecystokinin 8 (CCK8) evoke an increase in intracellular Ca 2ϩ , which in turn activates calmodulin, resulting in the phosphorylation of proteins on the enzyme-containing ves-icles.…”