EFFECTS OF OXIDANTS ON PROPERTIES OF FLUORESCENT CALCIUM INDICATORS

An increasing number of studies use calcium-sensitive fluorescent dyes to address the relationship between elevated levels of intracellular calcium and free-radical-mediated damage in a variety of pathophysiolo gical phenomena. The present study evaluates the effects of reactive o xygen species on tile spectral properties of widely used calcium probe s such as Fura-2 and Fluo-3. We found that both Fura-2 and Fluo-3 are rapidly inactivated by hydroxyl radicals and enzymatically inactivated by peroxidase/H2O2. This results in a decrease in the dynamic range o f sensitivity of both dyes to Ca2+, as well as in a decrease in the af finity of Fluo-3 for Ca2+. The data suggest that oxidation of the calc ium probes affects the measurement of calcium in vitro and may alter t he interpretation of in vivo data since the absence of or Small change s in the calcium fluorescence signal can be the result of probe deacti vation ion by free oxygen radicals rather than the lack of actual Ca2 changes. (C) 1998 Academic Press.