Propagation of a calcium pulse between osteoblastic cells.

Using rat calvaria cells in primary culture monolayers and bone-like nodules, and isolated rat osteosarcoma cells, we show via laser scanning confocal microscopy and fluorescent indicator fluo-3/AM, that mechanical perturbation of a cell results in a transient increase (pulse) of measured intracellular calcium concentration that propagates from cell to cell, even between cells connected only by a thin process. The calcium pulse does not occur in the mechanically perturbed cell in calcium-free bathing medium, nor is there pulse propagation under this condition. Halothane, which blocks gap junctions, inhibits propagation. Propagation velocity does not decrease with successive cell to cell steps. These observations suggest the existence of a self-regenerating calcium signaling mechanism that may be based on a form of calcium-induced calcium release.