Lectin Histochemistry to Study Nerve-induced Exocytosis from Rabbit Submandibular Glands.

Abstract

In situ carbohydrate binding of the secretory granules in 3 cell types from rabbit submandibular glands (acini, granular tubules and intercalary ducts) with labeled lectins has been used to provide markers for the secretory changes that can be induced in the cells by prolonged parasympathetic or sympathetic nerve stimulation. This work has confirmed that parasympathetic stimulation causes exocytosis from acini and granular tubules and sympathetic stimulation causes a less extensive degranulation of acini without any apparent change to granular tubules. These studies have also demonstrated that granules in the intercalary ducts are more clearly revealed by lectin bindings than by more conventional histological methods used previously. This has shown that neither parasympathetic nor sympathetic impulses induce discernible exocytosis of granules from intercalary ducts, so it is a question as to whether 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 stimulation, there was an accentuation of Golgi-like staining in acinar cells, which suggests that replenishment of the secretory glycoproteins had already begun by means of protein synthesis and glycosylation. Despite some loss of acinar secretory material with sympathetic stimulation, no corresponding accentuation of Golgi-like staining was seen at that time.