The fine structural localization of adenosine triphosphatase activity on the taste bud in the fungiform papillae of the rat.

The localization of Mg++ activated adenosine triphosphatase (ATPase) activity in rat fungiform taste buds was demonstrated by electron microscopic histochemistry. Reaction product was found on the cell membrane of the taste cells, but not within their cytoplasm. Especially strong reaction occurred in the taste pore. Besides, enzymes were observed in axon-Schwann cell and axon-type I cell interspace, but not in the contacts of the nerve fiber and type II cell. The taste bud could well be distinguished from the surrounding epithelium by the existence of the reaction product. ATPase activity was absent at the synaptic portion where type III cells faced nerve fibers. No reaction product was seen along the basal lamina. In fungiform buds, the nerve fibers were frequently shown to make contact with each other, and these sites were devoid of deposits for ATPase.