M. Ransjo et al., MONOCLONAL-ANTIBODIES AGAINST THE PUTATIVE DIVALENT CATION-RECEPTOR THAT IS LOCATED ON PARATHYROID CELLS DO NOT STAIN ISOLATED RAT OSTEOCLASTS, Calcified tissue international, 54(4), 1994, pp. 274-277
It has been reported that osteoclastic function is regulated by calciu
m-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-re
ceptor that has been demonstrated on parathyroid cells. Studies with f
ura-2 loaded adherent single cells showed that an increase in extracel
lular 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 cou
rse of the [Ca2+]i increase varied considerably from cell to cell. Les
s than half of the cells responded with a rapid transient increase whe
reas the rest responded with a slow increase that reached a plateau wi
thin 1-2 minutes. When [Ca2+]e was changed back to 0.5 mM, a slow decr
ease in [Ca2]i was monitored. Immunohistochemical staining with two di
fferent monoclonal antibodies, recognizing the putative Ca2+ receptor
on parathyroid cells, did not indicate any staining on freshly isolate
d rat osteoclasts. Thus, our data demonstrate that an increase in [Ca2
+]e causes an elevation of [Ca2+]i in osteoclasts. This increase is no
t mediated via the putative cation-receptor found on parathyroid cells
.