Abstract
31P-nuclear magnetic resonance spectra of superfused cerebral tissues were obtained under normal, hypoglycaemic and hypoxic conditions. Concentrations of free intracellular magnesium were calculated from differences in chemical shifts between the .alpha.- and .beta.-resonances of the nucleoside phosphates. Control levels of 0.33 mM were significant increased to 0.52 mM in hypoglycaemia and to 0.57 mM in severe hypoxia. Removal of calcium from the superfusing medium increased the free intracellular Mg2+ concentration to 0.63 mM.