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Ultrastructural localization of a tartrate‐resistant acid ATPase in bone
Author(s) -
Reinholt Finn P.,
Widholm Silwa Mengarelli,
EkRylander Barbro,
Andersson Göran
Publication year - 1990
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650051009
Subject(s) - immunolabeling , acid phosphatase , bone resorption , osteoclast , chemistry , resorption , immunogold labelling , ultrastructure , v atpase , tartrate resistant acid phosphatase , bone remodeling , bone cell , microbiology and biotechnology , extracellular , atpase , anatomy , biochemistry , biology , medicine , enzyme , endocrinology , immunohistochemistry , in vitro
Osteoclasts are effector cells in bone breakdown, and the active bone resorption is confined to the ruffled border zone of these cells. An acid milieu is maintained in this zone which is probably a prerequisite for bone resorption. Tartrate‐resistant acid phosphatase (TRAP) activity has been recognized as a characteristic property of osteoclasts and in several studies proposed as a cytochemical marker of osteoclasts. We have previously isolated and characterized a tartrate‐resistant and iron‐activated acid ATPase (TrATPase) from rat bone, the enzyme being a member of the TRAP family. In the present study the ultrastructural localization of this enzyme was delineated by employing immunogold technique on low temperature‐embedded maxillar rat bone. Intensive immunolabeling was seen on the bone surfaces facing the ruffled border zone while lower amounts of marker were seen in adjacent bone areas, that is, on the bone surfaces facing the clear zone and deeper into the bone. Within the osteoclasts gold markers were observed mainly in vesicular structures interpreted as lysosomes. Immunolabeling was also observed in the recently described endocytic cells located near osteoblasts and osteoclasts. Also in these cells, the marker was confined to lysosomelike structures. The amount of label in bone facing osteoblasts was low, as was the amount within osteoblasts. Our observation of extracellular localization, in particular accumulation of TrATPase in bone matrix facing the ruffled border area of the osteoclasts, favors the view that the enzyme is exported to areas of active bone resorption, thereby indicating a potential role for the enzyme in this process.