The EFFECTS OF SUBSTANCE P AND RELATED PEPTIDES ON Α‐AMYLASE RELEASE FROM RAT PAROTID GLAND SLICES

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.

Section: Discussionmentioning

confidence: 99%

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

Anderson¹,

Garrett²,

Johnson³

et al. 1984

“…In certain tissues such as guinea-pig ileum and rat parotid gland, physalaemin is invariably more potent than SP, whilst eledoisin and kassinin are less active (Hanley & Iversen, 1980;Brown & Hanley, 1981;Gater et al 1982). In other tissues, however, the reverse order of potencies has been observed (Erspamer, Falconieri Erspamer & Linari, 1977;Iversen, Lee, Sandberg & Watson, 1982;Bailey, Gater & Jordan, 1982) and it is possible, therefore, that different subpopulations of receptors mediate responses in these tissues.…”

Section: Effect Of Extracellular Phmentioning

confidence: 99%

The effects of substance P on histamine and 5‐hydroxytryptamine release in the rat

Fewtrell

Foreman

Jordan

et al. 1982

352

128

SUMMARY1. Substance P (SP) induces histamine release from isolated rat peritoneal mast cells at concentrations of 0-1-10 /tM.2. Inhibitors of glycolysis and oxidative phosphorylation prevent the release of histamine induced by SP. 3. Cells heated to 47 'C for 20 min release histamine when treated with an agent causing cell lysis but fail to release histamine in response to SP.4. SP does not release histamine by interacting with cell-bound IgE.5. Histamine release by SP is rapid, with more than 90 % of the response occurring within 1 min of the addition of the peptide to mast cells at 37 'C. 6. Substance P, unlike antigen-antibody or compound 48/80, does not show enhanced release of histamine when calcium (0 1-1 mM) is present in the extracellular medium but calcium increases the response to SP when the ion is added after the peptide. Extracellular calcium (01-1 mM), magnesium (1-10 mM) and cobalt (0-01-0-1 mM) all inhibit SP-induced histamine release when added before the peptide.Pre-treatment of the cells with EDTA (10 mM) and washing in calcium-free medium inhibits the histamine release induced by SP.7. Histamine release induced by SP was optimum at an extracellular pH of 7-2. 8. A number of peptides structurally related to SP were examined for histaminereleasing activity. At the concentrations tested, the N-terminal dipeptides Lys-Pro and Arg-Pro, tuftsin, physalaemin, eledoisin, SP31,, Phe7]-SP6 -1 were all found to be inactive. The relative activities of the other peptides were:

“…Also the non-cholinergic, non-adrenergic field stimulus-evoked amylase release could be superimposed upon the VIP-evoked secretion even at 10-7 M-VIP. However substance P at 5 x 10-9 M (saturating concentrations of this peptide for amylase release in rat parotid are reported as 10-7-10-6 M: Brown & Hanley, 1981) did mimic all the effects of non-cholinergic, non-adrenergic field stimulation, including the 86Rb efflux, and there was a notable interaction between the non-cholinergic, non-adrenergic field stimulus responses and the response to exogenous substance P. Superfusion of substance P resulted in a marked secretion of amylase and 86Rb efflux, but in the continued presence of the agonist these effects rapidly returned to basal levels i.e. desensitization.…”

Section: V Gallachermentioning

confidence: 99%

Substance P is a functional neurotransmitter in the rat parotid gland.

Gallacher¹

1983

SUMMARY1. The technique of electrical field stimulation was employed to stimulate the intrinsic nerves ofisolated rat parotid gland fragments. Responses to field stimulation were recorded as changes in enzyme secretion (amylase release), radiolabelled ion fluxes (86Rb efflux) and electrophysiological effects (changes in acinar cell membrane potential and input resistance). All effects of field stimulation were abolished by the neurotoxin, tetrodotoxin (TTX).2. Selective use ofpharmacological antagonists revealed that both the sympathetic and parasympathetic nerves to this tissue were being excited by field stimulation. Importantly a significant component of the response to field stimulation persisted in the presence of combined autonomic receptor blockade by atropine, phentolamine and propranolol, i.e. due to release of a non-cholinergic, non-adrenergic neurotransmitter.3. The non-cholinergic, non-adrenergic neurotransmitter evoked amylase release, 86Rb efflux and electrophysiological effects seen as changes in acinar cell membrane potential and conductance, i.e. stimulus-permeability coupled.4. Two biologically active peptides, substance P (SP) and vasoactive intestinal polypeptide (VIP) were shown to evoke amylase release in the presence of combined autonomic blockade. VIP however did not evoke any increase in 86Rb efflux, i.e. not stimulus-permeability coupled. All the effects of the non-cholinergic, non-adrenergic transmitter were mimicked by substance P which evokes 86Rb efflux and electrophysiological effects in addition to amylase release.5. The non-cholinergic, non-adrenergic field stimulus effects on amylase release and 86Rb efflux were abolished or markedly attenuated in tissues which had been desensitized by prior exposure to exogenous substance P. In the presence of VIP, however, the non-cholinergic, non-adrenergic effects persisted and were apparently potentiated.6. Acute application of the neurotoxin capsaicin first stimulated a transient release of amylase and subsequently abolished the non-cholinergic, non-adrenergic field stimulus-evoked enzyme release.7. The putative substance P antagonist, D-Pro2, D-Trp7'9 substance P, reversibly blocked the response to both non-cholinergic, non-adrenergic nerve stimulation and exogenous substance P. It was demonstrated however that prolonged exposure to this 16-2 D. V. GALLACHER antagonist is associated with non-reversible and, importantly, non-specific neurotoxic effects.8. It is concluded that substance P or a closely related peptide is a functional neurotransmitter in the rat parotid gland.