LACK OF EFFECT OF TRANSMEMBRANE GRADIENT OF MAGNESIUM AND SODIUM ON REGULATION OF CYTOSOLIC-FREE MAGNESIUM CONCENTRATION IN RAT LYMPHOCYTES

The regulation of the intracellular concentration of Mg2+ ([Mg2+](i)) is not fully understood. The level of Mg in lymphocytes is a good pred ictor of total body Mg status. We measured [Mg2+](i) and total Mg in r at lymphocytes by using, respectively, the fluorescent Mg2+ indicator mag-fura-2 and atomic absorption spectrophotometry. The basal [Mg2+](i ) in rat lymphocytes was 328 +/- 23 mu mol/l. An elevation to 5 mmol/l or the removal of extracellular Mg2+ did not affect [Mg2+](i). A redu ction in extracellular Na+ did not influence [Mg2+](i) for 60 min. The total Mg concentration in lymphocytes also remained stable. Results s uggest that the permeability of the plasma membrane to Mg2+ is very lo w, and that Na+/Mg2+ exchange is not involved in the regulation of [Mg 2+](i) in rat lymphocytes. (C) 1997 Elsevier Science B.V.