Abstract
Cells of the junctional epithelium (JE) of rat molar gingiva were investigated for ultracytochemical demonstration of acid phosphatase (ACPase). Enzymatic activity was greatest in the intermediate zone of JE and localized in elements of the Golgi complex and a variety of lysosomal structures. Numerous primary lysosomes were revealed in the basal to intermediate cells, whereas secondary lysosomes (hetero-and autolysosomes) increased toward the coronal direction of JE. ACPase-positive lysosomes were often found in close proximity to or fused with the cytoplasmic vacuoles which were characteristically abundant in JE cells. Reaction product for ACPase was also demonstrated in some of these vacuoles. These observations strongly suggest that the vacuoles represent the heterophagosomes endocytizing the intercellular materials, and they constitute the “vacuolar” or endocytic-lysosomal system which might play an important role for defense mechanism by JE cells and presumably for catabolic processes in these cells, as well.
