CONFOCAL AND ELECTRON-MICROSCOPY TO CHARACTERIZE SIALOGLYCOCONJUGATESIN MOUSE SUBLINGUAL GLAND ACINAR-CELLS

Double lectin labeling for confocal microscopy and lectin-protein A-go ld binding for electron microscopy were applied to the mouse sublingua l gland in order to study surface and cytoplasmic sialoglycoconjugates . Per this purpose, serially cut sections were submitted to sialidase followed by incubation with lectins recognizing usually acceptor sugar s for terminal sialic acids. At the electron microscope level, the res idues subtended to sialic acid were individually identified on adjacen t sections by an indirect technique of labeling, whereas with confocal microscopy the above sugars were simultaneously visualized on the sam e section by a double staining method using fluorescein isothiocyanate (FITC)- and tetramethylrhodamine isothiocyanate (TRITC)-conjugated le ctins. Acinar cells were found to contain the terminal sequence sialic acid-beta-galactose in abundance while the sequence sialic acid-alpha -N-acetylgalactosamine appeared to be present in modest amounts. Both sialoglycoconjugates were homogeneously codistributed inside acinar ce lls. The combination with a saponification method also allowed the occ urrence of C-4 acetylated sialic acids linked to beta-galactose to be discovered, at the electron microscope level, on acinar cell secretory products.