FLUORESCENT MONITORING OF JURKATT CELL INTRACELLULAR MAGNESIUM DURINGMETABOLIC POISONING

Divalent cation movement characterizes the final common pathway of cel lular death from ischemic or metabolic injury. The influx of calcium i s an essential step in cellular death. We hypothesized that intracellu lar magnesium levels may change during the progression to cellular dea th. Verapamil-sensitive changes in free ionized intracellular Mg2+ ([M g2+]i) and Ca2+ ([Ca2+]i) levels were estimated in transformed T-lymph ocytes exposed to metabolic inhibitors. Separate experiments used a Mg 2+-sensitive fluoroprobe, mag-fura-2 (Ex 1,344, Ex 2,376, Em 500), and a Ca2+-sensitive fluoroprobe, fura-2 (Ex 1,340, Ex 2,380, Em 51 0). C hemical anoxia (sodium cyanide 1 mM, iodoacetic acid 10 mM) caused a g radual increase in [Ca2+]i (control 126 +/- 13 nM) to >1 mM by 1 0 min . This increase in [Ca2+]i was not affected by verapamil treatment. In separate experiments, [Mg2+]i levels were monitored during chemical a noxia. The specificity of mag-fura for Mg2+ over Ca2+ was reflected in the absence of a response to the lymphocyte Ca2+ mobilizer OKT-3. Unc orrected control [Mg2+]i levels (.4 +/- .1 mM) were not affected by th e combined cyanide-iodoacetate treatment. A small increase in mag-fura -2 fluorescence was noted, probably due to binding of Ca2+ to the fluo roprobe when [Ca2+]i exceeded 1 mM. Elimination of Ca2+ from the extra cellular buffer increased the resting estimate of intracellular [Mg2+] to 1.6 + .1 mM. These results indicate that 1) extracellular Ca2+ can interfere with the fluorescent determination of intracellular magnesi um concentration, and 2) intracellular free Mg2+ concentrations do not change in this cell line during chemical anoxia.