LECTIN HISTOCHEMISTRY TO STUDY NERVE-INDUCED EXOCYTOSIS FROM RABBIT SUBMANDIBULAR GLANDS

In situ carbohydrate binding of the secretory granules in 3 cell types from rabbit submandibular glands (acini, granular tubules and interca lary ducts) with labeled lectins has been used to provide markers for the secretory changes that can be induced in the cells by prolonged pa rasympathetic or sympathetic nerve stimulation. This work has confirme d that parasympathetic stimulation causes exocytosis from acini and gr anular tubules and sympathetic stimulation causes a less extensive deg ranulation of acini without any apparent change to granular tubules. T hese studies have also demonstrated that granules in the intercalary d ucts are more clearly revealed by lectin bindings than by more convent ional histological methods used previously. This has shown that neithe r parasympathetic nor sympathetic impulses induce discernible exocytos is of granules from intercalary ducts, so it is a question as to wheth er they are secreted more gradually during spontaneous secretion from the gland, as part of an ongoing process, independent of neural drive. The lectin histochemistry also revealed that, after parasympathetic s timulation, there was an accentuation of Golgi-like staining in acinar cells, which suggests that replenishment of the secretory glycoprotei ns had already begun by means of protein synthesis and glycosylation. Despite some loss of acinar secretory material with sympathetic stimul ation, no corresponding accentuation of Golgi-like staining was seen a t that time.