IMMUNOHISTOCHEMICAL EVIDENCE FOR THE EXISTENCE OF RAT CYTOSOLIC SIALIDASE IN RAT SKELETAL-MUSCLES

Histochemical evidence is required to demonstrate the presence of bioc hemically defined cytosolic sialidase. To meet this requirement? we ex amined the immunohistochemical localization of the enzyme in rat skele tal muscles. Sections of chemically fixed tissues were incubated with a polyclonal antibody raised against a synthetic peptide which corresp onded to a part of the enzyme protein. After incubation with the prima ry antibody, cryosections for fluorescence microscopy and resin sectio ns for electron microscopy were incubated with a fluorochrome- and col loidal gold-labeled secondary antibody, respectively. Immunofluorescen ce was diffusely distributed in the muscle fibers and was also found i n the perimysium and blood vessels. Many immunogold particles were sca ttered over the sarcoplasm, myofibrils, nucleoplasm, and matrix of mit ochondria. The immunogold particles were also found in the equivalent compartments of axons, Schwann cells, and cells of endomysium and bloo d vessels. The specificity of the primary antibody was elucidated by i mmunoblotting and an immunoprecipitation test. These findings clearly indicate that this type of sialidase is essentially located in the cyt osolic compartment. Consequently, the name, cytosolic sialidase, will be appropriate for this enzyme. Additionally it is indicated that this enzyme is also present in cells other than skeletal muscle fibers.