Prostaglandin E1 induced salivary secretion

Peroxidase secretion in rat submandibular glands induced by PGE2: role of cAMP and nitric oxide

Free radicals are associated with the appearance of disorders such as tumours, CNS alterations and inflammatory pathologies. Their levels are known to be increased in inflammatory diseases due to the activity of prostaglandins, which are related to protein secretion including enzymes. Peroxidase is an oral enzyme that is implicated in the defence of the oral cavity. In this paper, investigations of the effect and mechanism of the activity of prostaglandin E2 (PGE2) on peroxidase secretion of female rat submandibular glands are reported. Results showed that PGE2 significantly increased the secretion of submandibular peroxidase and that this effect was mediated by an increase of intracellular cAMP and nitric oxide synthase activation. This could imply that prostaglandins play a modulatory role in diseases where free radicals are involved.

Effects of indomethacin and prostaglandin E2 on amylase secretion by rat parotid tissue

Indomethacin increased the secretion by low concentrations of isoproterenol (IPR, 30-100 nM) and decreased the secretion by a high concentration of IPR (1 microM). Indomethacin also had opposite effects on the secretions induced by low and high concentrations of norepinephrine (NE). PGE2 did not affect the secretions induced by IPR and NE, but it reversed the stimulatory and inhibitory effects of indomethacin. These findings suggest that PG has a role in modulating the amylase secretory response of the rat parotid gland.

The modulatory effects of leukotrienes C4 and D4 on methacholine- and substance P-induced salivary secretion in rats

Although certain prostaglandins have been found to be inhibitory to nerve-evoked salivary flow, little is known of the effects the leukotrienes on salivary secretion. It was the purpose of this investigation to examine the effects of leukotrienes C4 (LTC4) and D4 (LTD4) on salivary secretion in the rat, using methacholine or substance P to induce basal secretion, and to test whether or not the observed effects of these eicosanoids were receptor-mediated by using the leukotriene receptor blocker FPL-55712. Methacholine (3 x 10(-4) M), or substance P (1 x 10(-6) M) was infused intra-arterially to stimulate secretion and saliva was collected separately from the parotid gland and the submandibular gland of anesthetized rats. LTC4 and LTD4 (each at 1 x 10(-9) to 1 x 10(-6) M) were found to reduce methacholine- and substance P-induced salivary flow in a dose-related manner. Salivary protein concentration and amylase activity were not significantly altered by the leukotrienes; however, arginine-esterase activity, stimulated by substance P, was increased by both leukotrienes. FPL-55712 (1 x 10(-8) M) was shown to reduce the inhibitory effects of LTC4 and LTD4, suggesting the involvement of leukotriene receptors for these agents in their action.

Actions of prostaglandins E2 and F2 alpha on release of 14C-labelled mucins from rat submandibular salivary acini in vitro

Mucin secretion was studied in vitro using well-characterized preparations of isolated acini. PGE2 significantly (p less than 0.05) increased release of [14C]-glucosamine labelled mucins at the highest concentration tested (10(-5) M), but was ineffective at lower doses (10(-9)-10(-6) M). PGF2 alpha had no effect on mucin secretion over this concentration range. PGE2 (10(-9)-10(-5) M) did not modify isoproterenol stimulated mucin secretion. The cyclooxygenase inhibitor indomethacin (10(-7)-10(-5) M) did not significantly inhibit either isoproterenol or noradrenaline stimulated mucin secretion. Thus it seems that, although PGE2 significantly increases mucin secretion at a high concentration, it is unlikely that prostaglandins play a major role in modulating beta-adrenergic stimulation of mucin secretion in rat submandibular acinar cells.

Modulating effects of prostaglandins on parasympathetic-mediated secretory activities of rat salivary glands

Exogenously administered PGE1 or PGE2, like atropine, markedly decreased both the flow and calcium concentration of parasympathetically evoked rat parotid saliva; PGF2 alpha was less effective. Despite the fact that prostaglandins greatly reduced the Ca concentration of nerve-evoked saliva, they did not change the glandular Ca concentration of either control or parasympathetically stimulated parotid glands. Prostaglandins (20 micrograms/kg, i.a.) decreased the Na or K concentration of nerve-evoked parotid saliva, but at lower doses had no significant effect. PGE1, PGE2, PGF2 alpha or atropine markedly decreased flow rates of similarly evoked rat submandibular saliva. Prostaglandins and atropine, however, decreased the Na concentration and increased the K concentration of parasympathetically evoked submandibular saliva. PGF2 alpha, like atropine, increased the Ca concentration of such saliva. Drug vehicle, ethanol, slightly decreased the flow of both parotid and submandibular saliva but not the ion secretion, Endogenous prostaglandins themselves may not play a role in secretory activities during parasympathetic nerve stimulation of rat salivary glands, since administration of indomethacin, and inhibitor of prostaglandin biosynthesis, prior to or during nerve stimulation did not significantly alter nerve-evoked salivary secretion, The mechanisms by which prostaglandins modulate secretory responses of salivary glands during parasympathetic stimulation are not understood.

Primary Sjogren syndrome: clinical and immunopathologic features

Primary Sjogren syndrome is an autoimmune condition in which dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) result from lymphocytic infiltration of lacrimal and salivary glands. Clinical and laboratory features of 60 primary Sjogren syndrome patients seen at our clinic during the past three years are presented. These patients illustrate the wide spectrum of extraglandular features that may occur as a result of lymphoid infiltration of lung, kidney, skin, stomach, liver, and muscle. They further emphasize the difficulty in classifying a patient as primary or secondary Sjogren syndrome (ie, sicca symptoms associated with systemic lupus erythematosus, rheumatoid arthritis, or scleroderma), particularly early in the disease course. As an initial step in understanding the pathogenesis, the lymphocytes that infiltrate the salivary glands and lymph nodes were characterized by using monoclonal antibodies that recognize distinct lymphocyte subsets and by using in vitro functional assays. These studies have demonstrated that affected tissues have infiltrates of T cells with helper/inducer activity and with a high frequency of "activation antigens." The immunohistologic techniques are useful in differentiating "benign" and "pseudolymphoma" lesions (both due predominantly to T cells) from non-Hodgkin lymphoma (usually due to B-cell infiltrates). Although there is no "cure" for primary Sjogren syndrome patient's symptoms may be significantly improved by measures aimed at prevention of ocular and dental complications and by the recognition of extraglandular features that may be amenable to specific treatment.

Essential fatty acid metabolism in diseases of connective tissue with special reference to scleroderma and to Sjogren's syndrome

Drugs which modify the conversion of essential fatty acids to prostaglandins and leukotrienes are the mainstays of treatment in rheumatology. Yet these drugs have little or no action in scleroderma or Sjogren's syndrome and under some circumstances may have adverse effects. Patients with scleroderma have been shown to have very high levels of circulating prostaglandins, coupled with depletion of the prostaglandin precursors, dihomogammalinolenic acid and arachidonic acid. Levels of the metabolites of arachidonic acid, 22:4n-6 and 22:5n-6, which have major roles in maintaining normal cell membrane characteristics were exceptionally low in both plasma and red cell membranes. Others have observed that various functions are highly resistant to normal actions of PGs in scleroderma. This raises the possibility that the high rate of PG formation in scleroderma may be beneficial, in compensation, and that clinical symptoms develop when PG precursors begin to be depleted. Red cell membrane fatty acids patterns in Sjogren's syndrome are almost identical to those in scleroderma. Placebo-controlled trials of supplementation with essential fatty acids have been found to be beneficial in both scleroderma and Sjogren's syndrome.