The impact of calcium buffering on the initiation and propagation of mechanically elicited intercellular Ca2+waves was studied using astrocytes loaded with different exogenous, cell membrane-permeant Ca2+chelators and a laser scanning confocal or video fluorescence microscope. Using an ELISA with a novel antibody to BAPTA, we showed that different cell-permeant chelators, when applied at the same concentrations, accumulate to the same degree inside the cells. Loading cultures with BAPTA, a high Ca2+affinity chelator, almost completely blocked calcium wave occurrence. Chelators having lower Ca2+affinities had lesser affects, as shown in their attenuation of both the radius of spread and propagation velocity of the Ca2+wave. The chelators blocked the process of wave propagation, not initiation, because large [Ca2+]iincreases elicited in the mechanically stimulated cell were insufficient to trigger the wave in the presence of high Ca2+affinity buffers. Wave attenuation was a function of cytoplasmic Ca2+buffering capacity; i.e., loading increasing concentrations of low Ca2+affinity buffers mimicked the effects of lesser quantities of high-affinity chelators. In chelator-treated astrocytes, changes in calcium wave properties were independent of the Ca2+-binding rate constants of the chelators, of chelation of other ions such as Zn2+, and of effects on gap junction function. Slowing of the wave could be completely accounted for by the slowing of Ca2+ion diffusion within the cytoplasm of individual astrocytes. The data obtained suggest that alterations in Ca2+buffering may provide a potent mechanism by which the localized spread of astrocytic Ca2+signals is controlled.