Influence of circulating catecholamines on protein secretion into rat parotid saliva during parasympathetic stimulation.

Abstract

SUMMARY1. Secretion ofproteins by rat parotid glands in response to parasympathetic nerve stimulation was studied in vivo during pentobarbitone anaesthesia.2. Parasympathetic stimulation (3-10 Hz) via the auriculotemporal nerve resulted in a copious flow of saliva low in protein. In contrast, sympathetic stimulation (5 Hz) via the cervical sympathetic trunk evoked saliva low in volume but high in protein.Nevertheless, the specific concentrations of amylase and peroxidase (mg/mg protein) and the ratio of amylase to peroxidase remained constant. Sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis revealed a single, rapidly migrating protein band of unknown identity in proportionately greater amounts in parasympathetic saliva than in sympathetic saliva.3. Bilateral adrenalectomy led to reduced amylase and peroxidase secretion in response to parasympathetic stimulation both on a mg/ml and a mg/mg protein basis. SDS gel electrophoresis also demonstrated the decrease in specific amylase concentration following adrenalectomy. The ratio of amylase to peroxidase, however, was not significantly affected. Administration of 6-hydroxydopamine 17-72 h prior to adrenalectomy caused no further reduction in the secretion of amylase and peroxidase.4. Chronic sympathectomy of 2-5-4 months duration resulted in an increased protein secretion (mg/ml) by the parotid gland in response to parasympathetic stimulation. This increase was only slightly reduced by bilateral adrenalectomy. However, as observed in non-sympathectomized rats, adrenalectomy caused a significant reduction in the specific concentrations of both amylase and peroxidase, but did not affect the amylase to peroxidase ratios.5. We conclude that parasympathetic nerve stimulation of rat parotid glands after overnight starvation causes secretion of proteins in proportions similar to, but in significantly lower concentrations than those found in sympathetic saliva. Circulating catecholamines, however, influence the amount of amylase and peroxidase secreted 6-2 L. C. ANDERSON AND OTHERS by the rat parotid gland in response to parasympathetic nerve stimulation and account for most of the increased secretion of these enzymes following chronic sympathectomy.

Secretion of Parotid Acinar Granules in Rats During Reflex Stimulation After Chronic Sympathectomy

“…One possible explanation for our findings is suggested by the recent observation that, even under anaesthesia, a degree of catecholamine circulating in the blood can influence the secretion of amylase on parasympathetic nerve stimulation of rat parotid glands, especially from glands made supersensitive by chronic sympathectomy (Anderson et al 1984). Furthermore, circulating catecholamines have been found to influence parotid acinar secretion in conscious rabbits (Gj6rstrup, 1980).…”

“…This is unlikely to be a consequence of metabolic and adaptational alterations leading to a changed role for parasympathetic nerves, since parasympathetic nerve stimulation per se of chronically sympathectomized glands (Anderson et al 1984) was not associated with similar evidence of degranulation.…”

Influences of Short‐term Sympathectomy on the Composition of Proteins in Rat Parotid Saliva

“…Salivary concentrations of PRP have been found to be altered by systemic administration of isoprenaline and propranolol, as mentioned earlier; we have now shown that they are also influenced directly by sympathetic nerves since removal of the nerves leads to a decrease in PRP secretion upon parasympathetic stimulation. The increase in amylase as a proportion of secreted protein was not seen following chronic sympathectomy (Anderson et al 1984), thus this change may be restricted to an early phase following sympathectomy, but a time-based study will be required to confirm this.…”

“…Protein concentrations of saliva were determined both by the Lowry assay (Lowry, Rosebrough, Farr & Randall, 1951) and absorbance at 215 nm (abs2l5nm) using a human albumin/globulin standard (Sigma). Amylase activity was assayed by the method of Bemfeld (1955) and converted to weight equivalents of amylase (Loyter & Schramm, 1962 (Schneyer & Hall, 1966; Anderson, Garrett, Johnson, Kauffman, Keller & Thulin, 1984;Asking & Emmelin, 1985). The increased amylase:protein and Lowry protein:abs2l5nm (L:A) ratios of saliva from sympathectomized glands indicate that the proportions of different proteins in parasympathetically evoked saliva are altered by sympathectomy.…”

Acinar degranulation in the rat parotid gland induced by neuropeptides

“…The rats were provided with a femoral venous catheter and fitted with a tracheal cannula and a rectal thermometer; body temperature was maintained at 38 "C by a thermostatically controlled blanket. In order to exclude cholinergic and adrenergic influences or the action of circulating catecholamines (Anderson et al 1984;Malhotra & Wakade, 1987), if any, on the secretory response, atropine sulphate (Sigma), the a-adrenoceptor blocker phentolamine mesylate (Ciba Geigy) and the P-adrenoceptor blocker propranolol hydrochloride (Sigma) were injected through the femoral venous catheter (2 mg kg-I of each) as a precaution. The blockers were given 10 min before the start of the infusion.…”