NUCLEOSIDE PHOSPHATASE ACTIVITIES AND SUBMICROSCOPIC LOCALIZATION OF ADENOSINE TRIPHOSPHATASE ACTIVITY IN GUSTATORY EPITHELIUM

Phosphatase activities were histochemically examined in the gustatory region, using adenosine triphosphate (ATP), inosine triphosphate, ADP, AMP and Na-β-glycerophosphate as substrate, and p-chloromercuribenzoate as the inhibitor for ATPase. With ATP as substrate, the reaction product was observed on taste hairs, the boundary of taste bud cells, subgemmal nerve fibers and capillary walls. The ATPase activity on the boundary of taste bud cells was differentiated from the other reactive sites and was proved to be substrate-specific and sulfhydryl-dependent. With an electron microscope, the reaction product of ATPase was localized mainly in the space between the membranes of taste bud cells and on the outer leaflets. The reaction product was also observed on intragemmal nerve fibers. The activity was present on the surface of the nerve fiber facing the dark cell, whereas it was almost absent on the site in contact with the light cell. It is suggested that dark cells are supporting elements and light ones are neuroepithelial elements.