Regulation of cation channels in cardiac and smooth muscle cells by intracellular magnesium

Magnesium regulates various ion channels in many tissues, including those of the cardiovascular system. General mechanisms by which intracellular Mg2+ (Mgi2+) regulates channels are presented. These involve either a direct interaction with the channel, or an indirect modification of channel function via other proteins, such as enzymes or G proteins, or via membrane surface charges and phospholipids. To provide an insight into the role of Mgi2+ in the cardiovascular system, effects of Mgi2+ on major channels in cardiac and smooth muscle cells and the underlying mechanisms are then reviewed. Although Mgi2+ concentrations are known to be stable, conditions under which they may change exist, such as following stimulation of β-adrenergic receptors and of insulin receptors, or during pathophysiological conditions such as ischemia, heart failure or hypertension. Modifications of cardiovascular electrical or mechanical function, possibly resulting in arrhythmias or hypertension, may result from such changes of Mgi2+ and their effects on cation channels.