LOCALIZED CALCIUM SIGNALING IN MULTINUCLEATED OSTEOCLASTS

Localized intracellular Ca2+ ([Ca2+](i)) pulses, fluctuations, and rep etitive spikes were detected in multinucleated rabbit osteoclasts in t he presence of serum and in response to calcitonin using the fluoresce nt calcium indicator fluo-3 and a laser scanning microscope. We observ ed that these [Ca2+](i) changes were often restricted within a region of the cell body or propagated from the initial region of occurrence t o other parts of the cell body but not to all parts. These observation s suggest the existence of significant barriers to Ca2+ transport betw een different cytoplasmic regions of the osteoclast. To further invest igate this phenomenon, we mechanically perturbed different cellular re gions by touching locally with a micropipette. This usually induced a local increase in cytosolic and nuclear free [Ca2+](i). In some cases there was propagation of the [Ca2+](i) increase to other regions but w ith part of the cell body not affected. Those regions of the cell body to which the [Ca2+](i) increase did not propagate had a [Ca2+](i) res ponse to a direct mechanical perturbation. Our data show that osteocla sts can have different [Ca2+](i) activities in apparently equivalent c ellular regions, no matter how generated. This suggests that there can be a number of spatially separate Ca2+ regulatory systems within an o steoclast cell body. (C) 1996 Wiley-Liss, Inc.