EFFECT OF EPIDERMAL GROWTH-FACTOR ON MAGNESIUM HOMEOSTASIS IN BC3H1 MYOCYTES

The acute effects of epidermal growth factor (EGF) on Mg2+ homeostasis were studied in differentiated BC3H1 myocytes. EGF produced a 48-fold stimulation of [H-3]thymidine incorporation into quiescent serum-starved cells in the presence of Mg2+, whereas insulin had no effect on [H-3]thymidine incorporation. The dose dependence of EGF-stimulated [H-3]thymidine incorporation was similar to that of EGF stimulation of Mg-28(2+) uptake. In cells loaded with the Mg2+-sensitive fluorescent indicator, Mag-fura-2, intracellular Mg2+ concentration ([Mg2+]i) increased after exposure to EGF after a 5-min lag; a similar lag was routinely observed before the stimulation of Mg-28(2+) uptake by EGF. In control studies, cytosolic free Ca2+ levels and intracellular pH (pH(i)) were unchanged during 20 min of exposure to EGF. These results suggest that [Mg2+]i in BC3H1 cells is regulated by EGF. This regulation is not mediated by changes in pH(i) or intracellular Ca2+ concentration and may constitute an important event in the physiological response of these cells to EGF. The results are discussed within the context of cellular regulation of Mg2+ homeostasis.