Effects of intracellular free magnesium on calcium current in isolated cardiac myocytes
Magnesium ions play a fundamental role in cellular function, but the effects of changes in the concentration of intracellular ionized magnesium ([Mg2+](i)) on cell physiology have only recently received experimental attention. Increasing [Mg2+](i) from 0.3 to 3.0 mM in cardiac cells by internal perfusion has only small effects on the basal voltage-gated calcium current (I(Ca)) or on I(Ca) elevated by dihydropyridine calcium channel agonists. In contrast, I(Ca) elevated by cyclic adenosine monophosphate (cAMP)-dependent phosphorylation decreases by more than 50 percent. The effect of [Mg2+](i) is not due to changes in the concentration of cAMP or in the velocity of phosphorylation but rather appears to be a direct effect on the phosphorylated channel or on channel dephosphorylation.
White, Richard E. and Hartzell, H. C., "Effects of intracellular free magnesium on calcium current in isolated cardiac myocytes" (1988). PCOM Scholarly Papers. 1113.