Localization and turnover of calcium in biominerals (otoconia, bone and teeth).

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The localization of pyroantimonate-precipitable calcium was examined in calcifying systems. Specimens were fixed by the pyroantimonate method and selectively decalcified by treatment with ammonium chloride. After this treatment, otolithic organs and young bones were easy to cut into sections and following results were obtained:1.The fixation with pyroantimonate and glutaraldehyde (two step method) resulted in better preservation of tissue and more precise localization of precipitaes than did the direct immersion of specimens in pyroantimonate and osmium tetroxide (one step method).2. In the endolymphatic sac of the tree frog, the precipitate was distributed around calcium carbonate crystals. When crystalline growth was accelerated, the precipitate increased in amount. These crystals were considered to grow by accretion.3. In the otolithic organs in the inner ear of the rat and guinea pig, the precipitate was found around otoconia where a silver methenamine-positive material existed.4. In bone of very young rats, the precipitate was frequently observed within the endoplasmic reticulum of obsteoblasts, and on vacuoles and the ruffled border of osteoclasts. The distribution of calcium pyroantimonate in decalcified bone was the same as that in undecalcified counterparts.5. The precipitates of calcium pyroantimonate were well retained and the fine structure of the tissue was well preserved after the treatment with ammonium chloride.6. The presence of calcium in the precipitates was confirmed by X-ray microanalysis and extraction with EGTA.