New Observations on the Alkaline Glycerophosphatase Reaction in the Papilla Foliata

The histochemical demonstration of alkaline glycerophosphatase in the papilla foliata of the rabbit's tongue was reported by Bourne (3) and by Baradi and Bourne (1). The aim of the present investigation was to record the speed of the histochemical reaction and the detailed distribution of the enzyme in this tissue. Fixation was carried out in the ice box using 85 per cent alcohol for 3 hours followed by absolute alcohol for another 3 hours. Sections were incubated in the Gomori substrate mixture for alkaline glycerophosphatase (6), and the cobalt-sulphide method was used for visualizing the calcium phosphate precipitated at the sites of the enzyme activity. After only 1 second's incubation, a very faint reaction was obtained, but it was visible only on careful microscopical examination. I t was localized in the most superficial layers of the epithelial lining of the upper /2~ of the lateral walls of the gutters separating two individual papillae. A reaction in the same area was obtained after 5 and 15 seconds' incubation (Fig. 2) but in both cases it was greatly intensified compared with the 1 second preparation, and could be seen with the naked eye. In these three preparations the reaction was obviously located between the cells and could have been in the cell membranes or in the intercellular substance, or both. After 45 seconds' incubation the reaction extended into the deeper layers of the epithelium to include those cells that directly overlie the taste buds (Fig. 3). In these deep layers of cells, in addition to a reaction which outlined the cells (Fig. 4 a), there was a peripheral granular cytoplasmic staining (Fig. 4b). After 2 minutes' incubation the reaction extended down to the cells lining the bases (lower 1/i) of the gutters where it followed the outlines of the cells (Fig. 5). Here also, there was a peripheral granular cytoplasmic staining. Increasing the incubation time to 45 minutes increased only the intensity