Distribution of magnesium in the arterial wall.

1. The Mg, Ca, Na and K content were determined in the rat tail artery in vitro under various experimental conditions.2. The arterial Mg could be varied selectively at a constant Mg by altering the content of intracellular compounds capable of forming complexes with Mg(2+) such as nucleoside-5'-triphosphates or citrate.3. The release of tissue Mg during incubation in Mg-free solutions was found to consist of a fast and a slow component. The size of the fast component was dependent on the original Mg. The size of the slow component was dependent on the content of intracellular compounds forming complexes with Mg(2+). The rate of efflux of the slow component could be increased by increasing Mg(2+), by removing external Ca, or by making the artery metabolically inactive.4. The results seem to indicate that Mg(2+) in metabolically active vascular smooth muscle cells is maintained at a level of ca. 10(-4)M.