Spatial and temporal Ca2+ signalling in articular chondrocytes.

Stimulation of pig articular chondrocytes with either bradykinin, fetal calf serum or the Ca(2+)-ATPase inhibitor thapsigargin induced increases of the cytosolic Ca2+ concentration. By computerized videoimaging, the spatial and temporal aspects of the Ca2+ signal were revealed at single cell level. The cell response depended on Ca2+ release from intracellular stores without significant contribution of Ca2+ influx. A great heterogeneity in the cell population was found with respect to the Ca2+ storage ability. The Ca2+ response initiated in a discrete subcellular region and then spread in a nondecremental fashion to involve the whole cytosol. Such a behaviour was independent of the stimulus applied, thus suggesting a functional heterogeneity of the intracellular Ca2+ stores involved. In the region from which the response started, local Ca2+ spikes were recorded, revealing a spatially restricted pulsatile activity.