Localization of ATP-hydrolyzing enzyme activity at pH 9.0 was examined using rat tail bones which had been treated with the perfusion decalcification technique. The lead citrate methods after Ogawa and Mayahara (1969) or Ando et al. (1981) were used for demonstration of enzyme activity, which was mainly present on the plasma membrane and in the intracellular granules of osteoblasts. Osteocytes and osteoclasts did not have any significant activity. The activity was resistant to EDTA-decalcification and stimulated not only by Mg++ions but also Ca++ ions. Neither levamisole nor sodium fluoride affected it. These findings showed that there was ATP-hydrolyzing activity which was not due to alkaline phosphatase in osteoblasts. Since this activity was stimulated by Ca++ ions, it seems to be identical with so-called Ca-ATPase.
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Fukushima et al. (1984) studied this question.