Monoclonal antibodies against the putative divalent cation-receptor that is located on parathyroid cells do not stain isolated rat osteoclasts.
It has been reported that osteoclastic function is regulated by calcium-induced alterations in cytoplasmic free calcium ([Ca2+]i), possibly through a specific receptor. We have investigated whether osteoclasts, isolated from neonatal rat long bones, possess the divalent cation-receptor that has been demonstrated on parathyroid cells. Studies with fura-2 loaded adherent single cells showed that an increase in extracellular Ca2+ ([Ca2+]e) from 0.5 mM to 10 mM resulted in an increase in [Ca2+]i in isolated rat osteoclasts, from a basal value of 94.7 +/- 16.2 to 150.6 +/- 22.4 nM (means +/- SEM; n = 14). The shape and time course of the [Ca2+]i increase varied considerably from cell to cell. Less than half of the cells responded with a rapid transient increase whereas the rest responded with a slow increase that reached a plateau within 1-2 minutes. When [Ca2+]e was changed back to 0.5 mM, a slow decrease in [Ca2+]i was monitored. Immunohistochemical staining with two different monoclonal antibodies, recognizing the putative Ca2+ receptor on parathyroid cells, did not indicate any staining on freshly isolated rat osteoclasts. Thus, our data demonstrate that an increase in [Ca2+]e causes an elevation of [Ca2+]i in osteoclasts. This increase is not mediated via the putative cation-receptor found on parathyroid cells.
Ransjö
M
M
Department of Oral Cell Biology, University of Umeå, Sweden.
Ljunghall
S
S
Wiberg
K
K
Backlin
K
K
Lerner
U H
UH
Johansson
H
H
Juhlin
C
C
Ljunggren
O
O
D000818:Animals; D000911:Antibodies, Monoclonal; D002118:Calcium / Q000032:analysis*; D002135:Calcium-Binding Proteins / Q000032:analysis* / Q000276:immunology; D002413:Cations, Divalent; D002469:Cell Separation; D002478:Cells, Cultured; D016257:Fura-2; D007150:Immunohistochemistry; D010010:Osteoclasts / Q000737:chemistry*; D010280:Parathyroid Glands / Q000737:chemistry* / Q000166:cytology; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling
D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D002413:Cations, Divalent; D002118:Calcium; D016257:Fura-2