The effects of high dose of parathyroid hormone on fetal osteoclasts and their precursors in vivo: an ultrastructural-cytochemical study.
BACKGROUND
It is not well known how the immediate precursors of osteoclast develop into osteoclasts in the fetus. This ultrastructural-cytochemical study was designed to clarify the formation process of the osteoclasts and their increased activities in the fetal mouse limb buds after administration of high dose parathyroid hormone (PTH).


METHODS
Twenty-four or forty-eight hours after the high doses of PTH were injected into amniotic fluid of the pregnant C3H mice, the femoral limb buds of embryos were dissected out. Tartrate-resistant acid phosphatase (TRAP) reactions were performed while preparing specimens for electron microscopy.


RESULTS
Both control and PTH-given preosteoclasts and osteoclasts exhibited TRAP-positivities in dense bodies and vesicles. As effects of PTH, a binucleated preosteoclast of tandem fashion was observed. More osteoclastic hyperactivities were observed in the diaphyseal bone marrow. An osteoclast with a large cytoplasm exhibited two sets of clear zones and ruffled borders. Some osteoclasts demonstrated prominent amoeboid figures, while other osteoclasts developed large cytoplasmic vacuoles, which contained pieces of calcified chondroid bars.


CONCLUSIONS
Our results revealed the progression of maturation from young preosteoclasts to osteoclasts. An existence of a peculiar binucleated preosteoclasts suggested one of the processes for multinucleation of the osteoclast. Quite remarkable osteoclastic hyperactivities were obviously the effects of high dose PTH. Our results also indicated the endophagocytic ability of the osteoclast. How PTH affected the osteoclasts and their precursors in the diaphyseal bone marrow can be speculated.
Isaki
H
H
Department of Orthopedic Surgery, Keio University School of Medicine, Tokyo, Japan.
Hanaoka
H
H
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D007527:Isoenzymes / Q000378:metabolism; D018878:Limb Buds / Q000196:embryology; D051379:Mice; D008809:Mice, Inbred C3H; D008854:Microscopy, Electron; D010010:Osteoclasts / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D010281:Parathyroid Hormone / Q000494:pharmacology*; D000071681:Tartrate-Resistant Acid Phosphatase
D007527:Isoenzymes; D010281:Parathyroid Hormone; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase