An electron microscopic cytochemical study was carried out to investigate the precise mechanisms for absorption of organic bone matrix components during bone resorption induced by parathyroid hormone. Transplantation of the parathyroid
tissue
was
done into medullary cavity of the tibia in the rats, which were examined 1, 2 and 4 days after the operation, employing horseradish peroxidase as a soluble protein tracer. The tibial bone were extirpated and examined by scanning and
transmission electron microscopy with cytochemical procedures.
@ES The results obtained were summarized as follows
@EN Intravenously-injected peroxidase was filled the osteoid layer and penetrated into the osteocyte lacunae and canaliculi, but did not enter the mineralized bone matrix, Whereas bone cells of resting state rarely took up exogenous
peroxidase, activated osteoblasts and osteoclasts treated with parathyroid hormone actively endocytosed peroxidase in pinocytotic coated vesicles, tubular structures and vacuoles. They also formed endocytotic vacuoles containing
peroxidase
in the Golgi area. The osteocytes treated with parathyroid hormone did not changed endocytotic activity. The results strongly suggest that both osteoblasts and osteoclasts be able to degrade and resorb bone matrix organic components
during
bone resorption induced by parathyroid hormone.
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