ISSN:
1432-0878
Keywords:
Osteoclasts
;
Calcitonin
;
Bone resorption
;
Acid phosphatase
;
Autophagocytosis
;
Electron microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Osteoclasts from the tibial metaphyses of young rats treated with porcine calcitonin were studied by electron microscopy. The animals were sacrificed 1 1/2, 4, 8 or 12 hours after injection of the hormone. In survey sections examined by light microscopy the osteoclasts appeared smaller than in control animals. At the ultrastructural level the osteoclasts showed the following alterations: 1) The typical ruffled border was absent. 2) Acid phosphatase was not present in the extracellular space between cell and bone. 3) The number of large vacuoles was decreased and there was no local accumulation of vacuoles in the cytoplasm. 4) The vacuoles did not contain bone crystals. 5) Vacuoles with cell organelles were increased in number. The majority of these vacuoles were identified as autolysosomes because they contained acid phosphatase and the enclosed cell organelles were partially digested. The above changes were present at all time intervals studied. The findings suggest that calcitonin decreases or inhibits bone resorption by osteoclasts. A decreased function of the osteoclasts may contribute to the hypocalcemic effect of the hormone. The increased number of autolysosomes is evidence of an enhanced autophagocytosis. Possible origins of the autolysosomes in osteoclasts are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00307190
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