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.
Available at: http://works.bepress.com/richard_white/49/