HISTOCHEMICAL EXAMINATION OF ADENOSINE NUCLEOTIDASES IN THE DEVELOPING RAT SPINAL CORD : POSSIBLE INVOLVEMENT IN AN ENZYMATIC CHAIN OF ATP DEGRADATION

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In an attempt to characterize the membrane-associated Ca^<2+>-ATPase activity in the roof and floor plates of the developing rat spinal cord (36), the effect of quercetin, a potent inhibitor of Ca^<2+>-transporting ATPase was histochemically examined. Histochemical localization of ADPase and AMPase activity was also investigated in relation to possible involvement in the enzymatic hydrolysis of ATP. When tissue specimens were incubated in media containing quercetin at a concentration of 0.1 or 0.5 mM, the Ca^<2+>-ATPase activity in both roof and floor plates appeared to be diminished, in a concentration-dependent manner, as seen underlight microscopy. The inhibitory effect of quercetin was clearly evident in the floor plate. ADPase activity was also noted in both the roof and floor plates, particularly in the roof plate. Electron microscopic study revealed that the ADPase activity was mainly localized in the lateral and luminal plasma membranes of these plate-forming cells, resembling the cytochemical localization of Ca^<2+>-ATPase activity. There was, however no evidence of histochemical activity of AMPase in the developing spinal cord. These findings indicate that, in addition to activity of Ca^<2+>-transporting ATPase, the roof and floor plate-forming cells during embryonic development may possess ecto-nucleotidases which hydrolyse ATP to AMP.
日本組織細胞化学会の論文