Synthesis and secretion of amylase in the rat parotid gland following autonomic nerve stimulation in vivo

Abstract

Parasympathetic and sympathetic nerve stimulation in vivo, individually and in combination, was used to study secretion and synthesis of amylase in the rat parotid gland. After 30 min with sympathetic nerve stimulation (3 Hz) a decrease in glandular amylase was seen, which corresponded approximately to the salivary output. On the other hand, after parasympathetic stimulation (10 Hz), chosen to obtain comparable amylase output, there was no decrease in glandular amylase, which points to synthesis during such activation. Experiments with incorporation of [3H]leucine, reflecting amylase synthesis, showed that both types of nerve stimulations increased such uptake in parotid protein. These results indicate that beside sympathetic activity, which is the main stimulus for granular amylase secretion, parasympathetic nerve impulses can evoke considerable amylase secretion because amylase synthesis is stimulated and amylase is rapidly available from a special, possibly non-granular pool. As expected from previous experiments an augmentation of amylase secretion was found, and the present experiments also indicated an augmentation at the level of synthesis when the two nerves were stimulated at the same time.

Acinar degranulation in the rat parotid gland induced by neuropeptides

“…The present response to neurokinin A seems to be the consequence of vesicular secretion. The possibility of a non-granular release of proteins in the rat parotid gland was demonstrated some time ago by Garrett & Thulin (1 975) in response to parasympathetic stimulation (at 10 Hz or less in the absence of receptor blockade) and when this was further explored, the release was found to be accompanied by increases in protein synthesis (Asking & Gjorstrup, 1987;. In contrast, sympathetic stimulation induced acinar degranulation without concomitant restoration of the amylase gland content under conditions where the amylase output was in the same range as that induced in response to parasympathetic stimulation.…”

Non‐adrenergic, non‐cholinergic influences on parotid acinar degranulation in response to stimulation of the parasympathetic innervation in the anaesthetized rat

“…Prolonged stimulation of the parasympathetic innervation at a frequency of 10 Hz or less has been reported to cause neither acinar degranulation nor loss in content of amylase activity in the parotid gland of the non-atropinized rat (Garrett & Thulin, 1975;Asking & Gjorstrup, 1987;Asking & Proctor, 1989). Therefore, amylase appearing in the parasympathetic parotid saliva under these experimental conditions is thought to follow the constitutive pathway, where proteins move from the Golgi to the cell surface in small vesicles as fast as they are formed (Kelly, 1985).…”

Effects of Reducing Submandibular Blood Flow on Secretory Responses to Parasympathetic Stimulation in Anaesthetized Cats

“…It is therefore possible that the release of preformed protein is relatively insensitive to deprivation of nutrients and that depletion of the granule population was too slight to be reflected in any reduction in protein output during successive periods of stimulation. Alternatively, it could be occurring entirely via the constitutive vesicular route under these conditions (Proctor, 1998) involving no loss of granules at all and with secretion rapidly followed by resynthesis as has been reported to occur in the parotid gland of the rat (Asking & Gj orstrup, 1987). At higher frequencies of C-L stimulation vasoactive intestinal peptide (VIP) is released from the postganglionic nerve terminals in this gland (Andersson et al 1982), which potentiates secretion of protein (Ekstr om & Tobin, 1990) with nitric oxide implicated both pre-and postsynaptically (Buckle et al 1995;Edwards et al 1996).…”