A microspectrophotometric study on the physicochemical properties of antipyrylazo III injected into rat myoballs for measuring free magnesium ion.

The accurate measurement of the intracellular concentration of free magnesium ions ([Mg2+]i) is essential for evaluating the role of Mg2+ in cellular functions. Among the specific (compared to fluorescent indicators) metallochromic dyes, antipyrylazo III (APIII) appears to be most suitable for measuring such concentrations in vertebrate cells according to in vitro studies. In this work, the intracellular physicochemical properties of APIII as a Mg2+ indicator were investigated in the cultured rat myoball by means of a microspectrophotometric technique, in order to obtain an accurate measurement of [Mg2+]i.