USE OF LECTIN PROBES ON TISSUES AND SYMPATHETIC SALIVA TO STUDY THE GLYCOPROTEINS SECRETED BY RAT SUBMANDIBULAR GLANDS

We used a panel of nine lectins to detect the glycosylation patterns o f rat submandibular glycoproteins. Binding of lectins was assessed on tissue sections and on Western blots of electrophoretically separated glycoproteins from glandular extracts or sympathetic saliva. Histochem ical staining of tissue sections showed that two lectins (DBA and SBA) with affinity for terminal GalNAc residues were localized specificall y to acinar cells. In contrast, LTA and UEA-I (alpha Fuc-directed) and LFA (NeuAc-directed) bound exclusively to granular tubule cells. PNA and MPA (beta Gal-directed), LCA (alpha Man- and alpha Glc-directed), WGA (beta GlcNAc- and NeuAc-directed), and sWGA (beta GlcNAc-directed) bound to both acinar and granular tubule cells. On electroblot prepar ations, LEA, PNA, WGA, DBA, and SBA reacted with high molecular weight acinar mucin components both in glandular extracts and in saliva. LTA , UEA-I, LEA, PNA, MPA, LCA, WGA, sWGA, and DBA bound to lower molecul ar weight bands on blots known to contain granular tubular proteinases . Lectin binding to acini and granular tubules was reduced in sections and in most bands from glandular extracts after sympathetic nerve sti mulation. Out results show that (a) secretory glycoproteins from rat s ubmandibular acinar cells are non-fucosylated and contain abundant alp ha GalNAc and NeuAc and a small proportion of beta Gal in their oligos accharide side chains, and (b) alpha Fuc, NeuAc, beta Gal, and alpha G alNAc form the major carbohydrate moieties of the secretory glycoprote ins from granular tubules. The results confirm the considerable potent ial of lectin probes for studying glycoproteins in secretions and in t heir cells of origin.