A novel DIDS-sensitive, anion-dependent Mg(2+) efflux pathway in rat ventricular myocytes.

The aim of this study was to identify the existence of anion-dependent Mg transport systems in cardiac muscle. DIDS-sensitive and anion-dependent (either Cl(-)(o) or NO(-)(3o)) increases in [Mg(2+)](i) occurred during Mg(2+) loading conditions. Much larger elevations of [Mg(2+)](i) occurred under Cl(-)(o)-free conditions with 0.1 mmol l(-1) DIDS, compared to Cl(-)(o) replacement alone. All these effects were abolished in Mg(2+)(o)-free medium. These data suggest a novel Mg(2+)-anion symport for Mg(2+) efflux against the electrochemical gradient that is fueled mostly by the efflux of an endogenous anion (HCO(-)(3)?), but with a small contribution from intracellular Cl(-) probably supplied via the Cl(-)-HCO(-)(3) exchanger.