USE OF LECTIN-PROBES FOR CORRELATIVE HISTOCHEMICAL AND BIOCHEMICAL ASSESSMENTS OF THE GLYCOSYLATION PATTERNS OF SECRETORY PROTEINS, INCLUDING KALLIKREINS, IN SALIVARY-GLANDS AND SALIVA

Labelled lectins were used as probes to study the glycosylation and se cretion of submandibular glycoproteins not only in sections of fixed g lands but also in glandular extracts and in nerve-induced saliva, afte r electrophoretic separations and immobilization in nitrocellulose mem branes. In cats the glycoproteins in sympathetic saliva differed consi derably from those in parasympathetic saliva. In sympathetic saliva th ey were found to originate mainly from striated ducts, to some extent from demilunar cells and to a small extent from acinar cells, whereas in parasympathetic saliva they arose mainly from acinar cells and demi lunes and only to a small extent from striated ducts. In rat submandib ular glands sympathetic stimulation caused extensive depletion of lect in stainable granules from granular tubules. Corresponding strong bind ing occurred with the same lectins to constituents in saliva that ran between 25 and 35 kD on SDS gel electrophoresis and were shown to cont ain tissue kallikreins. Their binding patterns suggested that individu al kallikreins from the same gland may be glycosylated in different wa ys. This possibility was tested on five different kallikreins after se paration from submandibular extracts by isoelectric focussing. Lectin bindings on slot blot preparations of these kallikreins were tested be fore and after N-glycosidase F, sialidase or endo-alpha-N-acetylgalact osaminidase digestions. Results showed that, despite their close genet ic and structural similarities, the kallikreins are in fact differentl y sialylated and fucosylated and the novel finding that some contain O -glycosidically linked side chains as well as the anticipated N-glycos idically linked side chains was revealed. Thus, correlative histochemi cal and biochemical assessments of bindings with lectin probes has pro vided important new information about differences in the glycosylation patterns of individual glycoproteins stored within the same secretory granules.