Some metabolic activities in the spinal cord of the rat during embryonic development were investigated by using cytochemical techniques for calcium-dependent adenosine triphosphatase (Ca
2+-ATPase) and alkaline phosphatase (AlPase).
Under light microscopy, the roof and floor plates of the primitive spinal cord at embryonic day (E) 12 clearly showed high Ca
2+-ATPase activity, whereas the lateral plates, in contrast, had marked AlPase activity. In the later stages of development, the lateral walls also exhibited Ca
2+-ATPase activity. Under electron microscopy, reaction products for the Ca
2+-ATPase activity in the roof and floor plates were mainly localized in the lateral plasma membranes, including many cytoplasmic processes, of these plate-forming cells.
These findings indicate that the roof and floor plate-forming cells are different in enzyme activity from the proliferative cells of the lateral walls during embryonic development. The possible roles of Ca
2+-ATPase in the membrane activity of early differentiated neuroepithelial cells during the embryonic development of the spinal cord are discussed.
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