[Ultracytochemical localization of Ca++ATPase activity in human term amniotic epithelial cell]

In the human amniotic epithelial cell, intracellular Ca++ is known to play an important role in the initiation of parturition. Ca++ATPase is estimated to act on the regulation of the intracellular Ca++ concentration in amniotic epithelial cell. Therefore, to understand the Ca++ metabolism in human term amniotic epithelial cell, ultracytochemical localization of Ca++ATPase activity was investigated. At the same time, the ultracytochemical localization of Ca++ATPase was also compared with other phosphatases to confirm the specificity. Ca++ATPase activity was found to be positive on lateral plasma membrane of amniotic epithelial cell. The activity was strong at a 10mM Ca++ concentration. The activity was also found to be positive on the plasma membrane when 10mM Mg++ was used instead of Ca++. Acid phosphatase activity was positive on the lysosome of the amniotic epithelial cell. The other phosphatase activities appeared negative. These observations suggest that in the amniotic epithelial cell, Ca++ metabolism is active and the Ca++, entering into the cytoplasm, may flow out through the lateral membrane of the amniotic epithelial cell.