ISSN:
1432-0827
Keywords:
Osteoclasts
;
Plasma membrane vesicles
;
Calcium transport
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
,
Physics
Notes:
Summary Plasma membrane vesicles were prepared from chicken osteoclasts, and active calcium transport was demonstrated in a spectrofluorimetric assay using the fluorescent calcium concentration indicator, fura-2. Transport activity was inhibited by quercetin (10 μM), sodium vanadate (10 μM), and the anticalmodulin agents, compound 48/80 (20 and 200 μg/ml) and calmidazolium (10 and 20 μM). The transport rate (Vmax, 1.3 nmol/mg protein/min) was not altered in the presence of the protonophore, nigericin (1 μM), indicating that proton transport was not driving calcium transport. Release of accumulated calcium in the vesicles occurred with the addition of bromo-A23187 (5 μM) or ionomycin (5 μM). Increasing calcium transport occurred with increasing calcium concentration. Finally, the calmodulin content of the vesicles was demonstrated to be 54–134 U/mg protein. These results demonstrate that a calmodulin-sensitive, ATP-dependent calcium transporter is present in the osteoclast plasma membrane.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00334493
Permalink
