CONTRIBUTION OF CONFOCAL LASER-SCANNING MICROSCOPY TO GLYCOCHEMISTRY OF MOUSE AND RAT SUBMANDIBULAR GLANDS BY SINGLE AND DOUBLE LECTIN STAINING

The localization of individual glycosidic residues in the mouse and ra t submandibular glands was examined using confocal laser scanning micr oscopy (CLSM). For these organs we tested some procedures of fixation and embedding to better understand the distribution of some lectin-pro bes inside well preserved secretory cells and observed that fixation a nd inclusion steps did not influence appreciably the location and inte nsity of the reactive sites. The fixation mixture of 4% paraformaldehy de, 1% glutaraldehyde and 0.2% picric acid produced the most satisfact ory results. In specimens labeled with PNA-, Con A-, LTA-FITC and WGA- , DBA-TRITC lectins, the convoluted granular tubules (CGT) proved to b e composed of secretory granules with high-density lectin labeling. Th e complex organization of secretory glycocomponents within the granule matrix was further resolved by double labeling and dual scanning expe riments. Some lectins exhibited colocalization while others displayed differential localization providing information about the occurrence o f O- and N-linked glycoconjugates. The CLSM technique applied to fluor ochrome-conjugated lectins also revealed a more marked dimorphism in t he rat rather than in the mouse submandibular gland. In particular, th e male rat submandibular gland was found to consist of CGT heterogeneo us cell populations, while the mouse submandibular gland did not show glycochemical differences between cells. Female rats exhibited a lecti n profile very different from that of female mouse.