Abstract
Mg ions have been recognized as the important divalent cations for various physiological functions including the regulation of enzymatic activity, energy charge and signal transduction in cells. Recently, we have developed several types of novel Mg indicators, and we found that KMG-104 is a promising candidate for investigating intracellular Mg mobilization because of its high-sensitivity for Mg but not for Ca. The simultaneous measurement of Ca and Mg concentration with the combination of laser-photolysis of several caged compounds and dual-view imaging technique allows us to systematic investigation of divalent cation mobilization in cells. Transient increase of intracellular Ca and IP3 by photolysis induced no intracellular Mg concentration change in PC12 cells. This result indicates that Mg mobilization mechanism has no concern with Ca mobilization. Transient increase of intracellular Mg and Ca concentration was observed when FCCP, an uncoupler of oxidative phosphorylation at the inner membrane of mitochondria, was bath-applied. However, oligomycin, an inhibitor of ATP synthase, did not induce Mg and Ca concentration. These observations could be explained that intracellular Mg is not released from ATP during short-term exposure to oligomycin, and mitochondria are a plausible source of intracellular Mg release. We also observed that FCCP-induced intracellular Mg increase gradually returns to the basal level because of a Na/Mg ion exchanger on the cell membrane (Kubota et al. 2003). The simultaneous imaging of Ca and Mg ions will be revealed the cross talk of these important cations in single cells. [Jpn J Physiol 54 Suppl:S37 (2004)]
