Photorelease techniques for raising or lowering intracellular Ca2+.

The quantitative manipulation of intracellular calcium concentration ([Ca(2+)](i)) is a valuable instrument in the modern cell biologists' toolbox for unraveling the many cell processes controlled by calcium. I summarize here the major classes of photosensitive calcium chelators used to elevate or reduce [Ca(2+)](i), with an emphasis on their physicochemical properties and methods of calculating magnitudes and kinetics of effects on [Ca(2+)](i) of flashes and steady light, in order to encourage the choice of the best substance for particular applications. The selection and calibration of appropriate light sources, and procedures for introducing the chelators into cells, spatially restricting [Ca(2+)](i) changes, and measuring the profiles of [Ca(2+)](i) changes imposed by photolysis, are also described. The final section describes a selection of biological applications.