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 (ICa) or on ICa elevated by dihydropyridine calcium channel agonists. In contrast, ICa 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.
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology / Q000502:physiology*; D008564:Membrane Potentials; D010766:Phosphorylation; D011898:Ranidae; D016276:Ventricular Function
D007473:Ion Channels; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D008274:Magnesium; D007545:Isoproterenol; D002118:Calcium