Extracellular Ca 2+ sensing by the osteoclast

• Published in: Cell calcium (Edinburgh) Vol. 14; no. 4; pp. 271 - 277
• Main Authors: Zaidi, M., Alam, A.S.M.T., Huang, C.L.-H., Pazianas, M., Bax, C.M.R., Bax, B.E., Moonga, B.S., Bevis, P.J.R., Shankar, V.S.
• Format: Journal Article
• Language: English
• Published: Elsevier India Pvt Ltd 1993
• ISSN: 0143-4160; 1532-1991
• DOI: 10.1016/0143-4160(93)90048-B

An increasing number of cell types appear to detect changes in the extracellular Ca 2+ concentrationand and accordingly modify their function. We review recent evidence for the existence and function of such a mechanism in the osteoclast. Elevated external [Ca 2+] in the mM range reduces bone resorption and results in motile changes in the cells. These changes may partly result from elevations of cytosolic [Ca 2+] triggered through activation of a surface Ca 2+ receptor. Closer analyses of the increases in cytosolic [Ca 2+] associated with receptor activation are hindered by the action of this ion both as extracellular agonist and intracellular second messenger. Variations in the peak cytosolic [Ca 2+] response to external Ca 2+ with changes in cell membrane potential by K + and valinomycin establish a contribution from extracellular Ca 2+. Use of CIO 4 −, Ni 2+ and Cd 2+ as surrogate activators in low extracellular [Ca 2+] indicate a contribution from Ca 2+] release from intracellular stores as well. Such agonists also modify Ca 2+ redistribution in other systems, such as skeletal muscle. Thus, we may gain insights into osteoclast extra-cellular Ca 2+ detection and transduction from known features of more well-characterised cell systems.