EFFECTS OF INTRACELLULAR MAGNESIUM ON CALCIUM, POTASSIUM AND CHLORIDECHANNELS

Intracellular free magnesium activity approximates 0.6-0.8 mM. Variati ons in concentration around this physiologic range profoundly affect c urrent flow through calcium, potassium and chloride channels. These ef fects are exerted on both inwardly and outwardly directed currents and appear to be independent of the state of phosphorylation of the chann el. In the heart, these effects are manifested in changes in action po tential duration, which may help to explain postulated links between h ypomagnesemia and arrhythmias. In the kidney, effects of magnesium on ion channels may subserve a protective role and may explain how potass ium balance is altered in magnesium depletion syndromes.