CALCIUM SIGNAL INDUCED BY MECHANICAL PERTURBATION OF OSTEOCLASTS

Multinucleated osteoclasts from rabbit long bone, 1-6 days in culture, respond to mechanical perturbation with a transient increase of intra cellular calcium concentration ([Ca2+](i)), as measured with the fluor escent indicator fluo-3 on a confocal laser scanning microscope. In ex periments with different extracellular calcium concentrations (from 11 .8 mM to calcium-free), the incidence, the magnitude, and the duration of [Ca2+](i) responses decreases with decreasing bathing [Ca2+]. Foll owing mechanical perturbation, a thapsigargin-induced [Ca2+](i) respon se has a lower magnitude than the thapsigargin-induced response withou t mechanical perturbation. In thapsigargin-pretreated osteoclasts the mechanical perturbation-induced rise in [Ca2+](i) is larger and longer than in control cells. Ni2+ inhibits the incidence and decreases both the magnitude and the duration of the responses, while nifedipine, ve rapamil, and Gd3+ have no effect. These measurements show that rabbit osteoclasts transduce a mechanical perturbation of the cell membrane i nto a [Ca2+](i) signal via both a calcium influx and an internal calci um release. (C) 1995 Wiley-Liss, Inc.