Mag-indo-1/AM, a cell-permeable fluorescent indicator for Mg2+ and Ca2+ (Ex=340-390 nm, Em=410-490 nm), is used to determine intracellular Mg2+ and Ca2+ concentrations [1][2].

Measurement of intracellular Ca 2+: Incubate 3 mL cell suspension with 10 μM Mag-indo-1/AM for 15 min at 30℃. Centrifuge cells for 1 min at 500 rpm, resuspend in 5 mL isolation buffer (containing 1 mM CaCl 2), add 1 mM probenecid to prevent dye leakage, and store (Mag-indo-1/AM-loaded cells) at room temperature. Incubate at room temperature for 2 h, shake gently at 37℃ for 1.5 h, centrifuge, resuspend, and store at room temperature. Place a small portion of loaded cells in an experimental chamber on an inverted microscope. Measure fluorescence of Mag-indo-1/AM (Ex=340-390 nm, Em=410 and 490 nm [peak emissions of Ca 2+ bound and free forms]) using a photon counting system.