Mitogen-induced early increase in cytosolic free Mg2+ concentration in single Swiss 3T3 fibroblasts.
Events related to the early mobilization of Mg2+ in mammalian cells in response to external stimuli are not well characterized. We examined changes in cytoplasmic free Mg2+ concentrations ([Mg2+]i) after mitogenic stimulation in single mouse Swiss 3T3 fibroblasts, using digital ratio imaging microscopy of the fluorescent probe mag-fura-2. Stimulation with bombesin or epidermal growth factor (EGF) in combination with insulin led to a significant increase in mean [Mg2+]i levels from basal 0.22 mM to 0.29-0.35 mM after 30-60 min. The response showed some heterogeneity among individual cells with respect to the extent of the increase; approximately 10% of the cells showed no [Mg2+]i response. Bombesin or EGF alone induced a significant increase in [Mg2+]i but was less effective than when combined with insulin. In medium without added Mg2+, the increase in [Mg2+]i was considerably decreased, either with bombesin plus insulin or EGF plus insulin. These results provide direct evidence for the mobilization of Mg2+ as an early cellular response to growth factors.
Ishijima
S
S
Department of Biochemistry, Chiba University School of Medicine, Japan.
Sonoda
T
T
Tatibana
M
M
D016475:3T3 Cells; D000818:Animals; D001839:Bombesin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D016257:Fura-2; D007091:Image Processing, Computer-Assisted; D007328:Insulin / Q000494:pharmacology*; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism*; D051379:Mice; D013050:Spectrometry, Fluorescence
D007328:Insulin; D015759:Ionomycin; D004815:Epidermal Growth Factor; D008274:Magnesium; D001839:Bombesin; D002118:Calcium; D016257:Fura-2