Cytochemical identification of lysosomal system of the rat junctional epithelium.

Abstract

Structures taking part in the lysosomal system of rat junctional epithelium (JE) were evaluated by means of ultrastructural enzyme cytochemistry. Acid phosphatase (AcPase) and trimetaphosphatase (TMPase), both the representative lysosomal marker enzymes, were frequently detected in dense bodies which contained the homogeneous matrix and showed pleomorphic appearance. These activities were also often localized to the phagosomes with heterogeneous contents, the reaction of TMPase being much more intense than that of AcPase. Cisternal structures, most probably corresponding to GERL, also displayed AcPase activity and exhibited the close morphologic relationships with lysosomal structures. On the other hand, the localization of thiamine pyrophosphatase activity was almost limited to the innermost cisterna of the Golgi complex. Neither AcPase nor TMPase activity could be detected in the cytoplasmic vacuoles, which were characteristically numerous in rat JE and the multivesicular bodies.From the present findings, it is suggested that the lysosomal system in rat JE is composed of dense bodies (primary lysosomes), phagolysosomes (secondary lysosomes), and GERL and that some of those lysosomes are apparently derived from GERL. Different localization patterns of marker enzymes examined might reflect the enzymatic heterogeneity of various lysosomal elements.