Regulation of salivary kallikrein secretion in submandibular gland

Endoplasmic reticulum stress affects mouse salivary protein secretion induced by chronic administration of an α1-adrenergic agonist

Stress stimulates both the sympathetic-adrenomedullary and hypothalamus-pituitary-adrenal axes. Activation of these axes results in the release of catecholamines, which in turn affects salivary secretion. Thus, repetitive stimulation of the α₁-adrenergic receptor could be useful for studying the effects of chronic stress on the salivary gland. Salivary protein concentration and kallikrein activity were significantly lower in mice following chronic phenylephrine (PHE) administration. Chronic PHE administration led to significantly increased expression of the 78-kDa glucose-regulated protein, activating transcription factor 4, and activating transcription factor 6. Histological analyses revealed a decrease in the size of the serous cell and apical cytoplasm. These results suggest that repetitive pharmacological stimulation of the sympathetic nervous system elicits ER stress and translational suppression. In addition, PHE-treated mice exhibited a decrease in intracellular Ca²⁺ influx elicited by carbachol, a muscarine receptor agonist in the submandibular gland. The present findings suggest that chronic psychological, social, and physical stress could adversely affect Ca²⁺ regulation.

Voltage-Sensitive K(+) Channels Inhibit Parasympathetic Ganglion Transmission and Vagal Control of Heart Rate in Hypertensive Rats

Parasympathetic withdrawal plays an important role in the autonomic dysfunctions in hypertension. Since hyperpolarizing, voltage-sensitive K⁺ channels (K_V) hamper transmitter release, elevated K_V-activity may explain the disturbed vagal control of heart rate (HR) in hypertension. Here, the K_V inhibitor 3,4-diaminopyridine was used to demonstrate the impact of K_V on autonomic HR control. Cardiac output and HR were recorded by a flow probe on the ascending aorta in anesthetized, normotensive (WKY), and spontaneously hypertensive rats (SHR), and blood pressure by a femoral artery catheter. 3,4-diaminopyridine induced an initial bradycardia, which was greater in SHR than in WKY, followed by sustained tachycardia in both strains. The initial bradycardia was eliminated by acetylcholine synthesis inhibitor (hemicholinium-3) and nicotinic receptor antagonist/ganglion blocker (hexamethonium), and reversed to tachycardia by muscarinic receptor (mAchR) antagonist (atropine). The latter was abolished by sympatho-inhibition (reserpine). Reserpine also eliminated the late, 3,4-diaminopyridine-induced tachycardia in WKY, but induced a sustained atropine-sensitive bradycardia in SHR. Inhibition of the parasympathetic component with hemicholinium-3, hexamethonium, or atropine enhanced the late tachycardia in SHR, whereas hexamethonium reduced the tachycardia in WKY. In conclusion, 3,4-diaminopyridine-induced acetylcholine release, and thus enhanced parasympathetic ganglion transmission, with subsequent mAchR activation and bradycardia. 3,4-diaminopyridine also activated tachycardia, initially by enhancing sympathetic ganglion transmission, subsequently by activation of norepinephrine release from sympathetic nerve terminals. The 3,4-diaminopyridine-induced parasympathetic activation was stronger and more sustained in SHR, demonstrating an enhanced inhibitory control of K_V on parasympathetic ganglion transmission. This enhanced K_V activity may explain the dysfunctional vagal HR control in SHR.

Simultaneous parasympathetic and sympathetic activation reveals altered autonomic control of heart rate, vascular tension, and epinephrine release in anesthetized hypertensive rats

Sympathetic hyperactivity and parasympathetic insufficiency characterize blood pressure (BP) control in genetic hypertension. This shift is difficult to investigate in anesthetized rats. Here we present a pharmacological approach to simultaneously provoke sympathetic and parasympathetic transmitter release, and identify their respective roles in the concomitant cardiovascular response. To stimulate transmitter release in anesthetized normotensive (WKY) and spontaneously hypertensive rats (SHR), we injected intravenously 4-aminopyridine (4-AP), a voltage-sensitive K⁺ channel (K_V) inhibitor. A femoral artery catheter monitored BP, an ascending aorta flow-probe recorded cardiac output and heart rate (HR). Total peripheral vascular resistance (TPVR) was calculated. 4-AP-induced an immediate, atropine (muscarinic antagonist)- and hexamethonium (ganglion blocker)-sensitive bradycardia in WKY, and in both strains, a subsequent, sustained tachycardia, and norepinephrine but not epinephrine release. Reserpine (sympatholytic), nadolol (β-adrenoceptor antagonist) or right vagal nerve stimulation eliminated the late tachycardia, adrenalectomy, scopolamine (central muscarinic antagonist) or hexamethonium did not. 4-AP increased TPVR, transiently in WKY but sustained in SHR. Yohimbine (α₂-adrenoceptor antagonist) prevented the TPVR down-regulation in WKY. Reserpine and prazosin (α₁-adrenoceptor antagonist) eliminated the late vasoconstriction in SHR. Plasma epinephrine overflow increased in nadolol-treated SHR. Through inhibition of K_V, 4-AP activated parasympathetic ganglion transmission and peripheral, neuronal norepinephrine release. The sympathetic component dominated the 4-AP–HR-response in SHR. α₂-adrenoceptor-dependent vasodilatation opposed norepinephrine-induced α₁-adrenergic vasoconstriction in WKY, but not SHR. A βAR-activated, probably vagal afferent mechanism, hampered epinephrine secretion in SHR. Thus, 4-AP activated the autonomic system and exposed mechanisms relevant to hypertensive disease.

An analysis of submandibular salivary gland function with desipramine and age in female NIA Fischer 344 rats

Dry mouth is one of the major side effects of cyclic antidepressants, which are still a dominating group of psychotherapeutic drugs used in the treatment of depression. In this study we analyzed the effects of 28 day tricyclic antidepressant administration and the reversibility of this treatment following a 15 day washout period on different parameters in submandibular gland function in aging rats. We postulated that desipramine would decrease gland function, accented with age, and delay recovery in senescent animals. In contrast to body weight, desipramine had no effect on glandular wet weight. While glandular DNA synthesis was changed with age and treatment, the concentration of total membrane and soluble proteins was not affected. Flow rate was significantly changed with age, but desipramine increased salivary flow in the youngest animals only. Neither age nor treatment influenced salivary protein concentrations, but the total amount of proteins secreted, revealed perturbation with age. SDS- polyacrylamide gel analysis revealed changes in protein expression with treatment and age. Desipramine decreased epidermal growth factor (EGF) levels in all age groups, but increased the secretion of peroxidase and lysozyme. Analysis of total RNA showed a pronounced decrease with age. These data indicate that desipramine has profound effects on submandibular salivary gland function.

The role of endogenous bradykinin in blood pressure homeostasis in spontaneously hypertensive rats

1. The role of endogenous bradykinin in mean arterial blood pressure (BP) homeostasis was studied in spontaneously hypertensive (SHR) and normotensive (WKY) rats by the use of a bradykinin B2-receptor antagonist (BKant; Hoe 140, 11.6 micrograms kg-1) and converting enzyme (kininase II) inhibitor (captopril, 10 mg). To obtain a response to captopril that was induced through inhibition of kinin-degradation only and not through inhibition of angiotensin II-formation, the studies were performed on binephrectomized male rats to eliminate the renin-angiotensin system. 2. The role of the nitric oxide (NO) and the adrenergic systems were evaluated by the use of NO-synthase inhibitor (L-NAME, 0.3 g kg-1) and phentolamine (2 mg kg-1), respectively. 3. The rats were anaesthetized and pretreated with two injections of vehicle (PBS) or drugs spaced 5 min apart: PBS + PBS; BKant + PBS; PBS + L-NAME; BKant + L-NAME; or phentolamine + L-NAME. All rats were given captopril 15 min later. Time-control groups were treated with L-NAME but not captopril. 4. In WKY rats, captopril did not significantly alter BP in any of the groups. In the SHR-PBS + PBS group, on the other hand, captopril induced an immediate fall in BP (delta BP = -23 +/- 4 mmHg, P < 0.0017) which was completely blocked by BKant (delta BP = 2 +/- 2 mmHg) (P < 0.0011). L-NAME did not significantly alter the immediate hypotensive response to captopril but disclosed a later hypertensive reaction. In L-NAME + BKant-treated rats, both the hypotensive response and the late hypertension was abolished. In rats treated with phentolamine + L-NAME, the immediate fall in BP was not different from the controls whereas the late hypertension was absent. 5. BKant itself had no effect on basal BP in either WKY or SHR even when a 10 times higher dose was tested in a separate set of experiments. This was true also for conscious, nonnephrectomized SHR rats. 6. It was concluded that endogenous production of bradykinin was demonstrable through kininase II-inhibition in hypertensive but not in normotensive rats. However, this endogenous bradykinin did not play a role in basal BP homeostasis. The captopril-induced hypotension depended on kinin but, under the present conditions, not on NO as a mediator. The fall in BP induced a compensatory adrenergic hypertensive response which was revealed when the continuous NO-synthesis was blocked by L-NAME.

Differential secretion of proteins by rat submandibular acini and granular ducts on graded autonomic nerve stimulations

1. The influence of graded parasympathetic and sympathetic nerve stimulations on the secretion of protein from rat submandibular gland was studied. Peroxidase was used as a marker for the acini and rat tissue kallikrein (official nomenclature rK1) as the marker for granular ducts. Tonin (rK2) was also measured, and the ratio of rK2:rK1 was calculated as an indication of the cellular route of secretion. 2. Continuous parasympathetic nerve stimulation caused a copious flow of saliva that had a low protein content. The secretion of peroxidase (acini) showed a gradual moderate increase as the frequency increased. However, the concentrations of rK1 and rK2 (granular ducts) showed little change throughout, and the ratio of rK2:rK1 remained relatively constant. 3. Graded sympathetic stimulation was applied against a background of parasympathetic stimulation. Secretion of peroxidase was increased by the addition of 0.1 Hz continuous sympathetic stimulation. The amount increased thereafter up to 2 Hz, but showed no further increase if the stimulation was applied as bursts of 10 or 20 Hz. In comparison, the secretion of proteinase activity showed little change with superimposed continuous sympathetic stimulation, and the rK2:rK1 ratio was similar to that in saliva produced by parasympathetic stimulation alone. Sympathetic stimulation applied in bursts, however, caused a large increase in the secretion of proteinase activity, and with 20 Hz burst stimulation the rK2:rK1 ratio was indistinguishable from that of sympathetic saliva per se. There was an augmented secretion of both peroxidase and kallikrein when 20 Hz burst stimulation was combined with parasympathetic stimulation. The effects of sympathetic stimulation were abolished by alpha- and beta-adrenoceptor blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological regulation of the secretion of histatins and statherins in human parotid saliva

The small salivary phosphoproteins, histatins and statherins, have important functions in the oral cavity in terms of antimicrobial actions and regulation of calcium phosphate homeostasis. Neither the effects of various physiological stimuli on their secretion nor the nature of the efferent receptor involved in the stimulus-secretion coupling has been determined previously. These aspects are important for improved understanding of the secretory control of salivary proteins and may have implications regarding the effects of specific medications on salivary constituents and oral health. The effects of graded mechanical (chewing on short and long silicone tubings) and gustatory stimulation (0.5, 1.5, and 5.0% citric acid) on the secretion of histatins and statherins were studied in the presence and absence of adrenolytic agents (n = 10). In this model, secretory rates of both proteins increased with increases in flow rate, with 5.0% citric acid representing a particularly potent stimulus. Histatin and statherin secretory rates were significantly reduced by the beta 1-adrenolytic agent (histatins to 58 to 72% and statherins to 11 to 29% of that in corresponding control experiments), but not by the alpha 1-adrenolytic agent. Since the beta 1-adrenergic receptors played an important role in the stimulus-secretion coupling of these proteins, protective salivary functions in the oral cavity may be compromised during beta 1-adrenolytic treatment.

The release of glandular kallikrein from submaxillary glands of rats exposed to heat

The salivary flow elicited by phenylephrine was reduced in kininogen-deficient rats or by pretreatment of normal Wistar rats with HOE 140, a bradykinin antagonist. Salivary flow induced by substance P was similar in normal and kininogen-deficient rats. Phenylephrine released large amounts of kallikrein in saliva. Isoproterenol was less active while pilocarpine and substance P induced a small secretion of kallikrein. The saliva produced by anaesthetized rats in response to heat stress contained low levels of kallikrein. However a large depletion of the kallikrein content of submaxillary glands was observed in awake animals exposed to 36 degrees C and 40 degrees C for one hour. This depletion was suppressed by prazosin administered with a beta-adrenergic antagonist. Administered alone, these drugs had no effect, whereas atropine increased the depletion. The presence of kallikrein was observed in the oedema fluid which developed around the submaxillary glands in rats pretreated with atropine or exposed to 40 degrees C. A consumption of plasma kininogens occurred during heat exposure. The reflex-induced release of kallikrein during heat exposure is mainly controlled by sympathetic nerves through activation of both alpha and beta-adrenoreceptors. This release induces the formation of kinins which participate to the thermolytic salivation.

Pilocarpine-induced salivary secretion, kinin system and nitric oxide in rats

In anaesthetized rats, intraperitoneal injection of pilocarpine (0.1 to 1 mg.Kg-1) induced a dose-dependent flow of saliva. During salivation by pilocarpine (0.5 mg.Kg-1), the blood content of submaxillary glands was not significantly increased but the blood volume of the animals was reduced. The salivary flow rate induced by pilocarpine was similar in normal and kininogen-deficient rats. L-NG-nitro-arginine (L-NOARG, 35 mg.Kg-1), a nitric oxide synthesis inhibitor, increased the salivary flow elicited by pilocarpine (0.5 mg.Kg-1). L-NOARG did not modify the blood volume loss but decreased the blood content of the submaxillary glands. The volume of salivary secretion induced by isoproterenol (250 mg.Kg-1) was lower in kininogen-deficient rats than in normal rats. It was significantly reduced by HOE 140 (2 mg.Kg-1), a bradykinin antagonist. L-NOARG increased the salivary flow induced by isoproterenol during the ten first minutes of collection but suppressed it thereafter. We concluded that kinins are not involved in the stimulating effect of pilocarpine on rat salivary glands but these peptides would participate to the development of the salivation induced by isoproterenol in rats. Nitric oxide contributes to the control of the vascular tone in rat salivary glands. The influence of L-NOARG on salivation would be explained by its effects on blood pressure and vascular resistances.

Processing of epidermal growth factor in the rat submandibular gland by Kallikrein-like enzymes

Epidermal growth factor (EGF) is synthesized as a precursor which is processed intracellularly to a 6 kDa EGF in the rat submandibular gland. This gland contains very high amounts of kallikrein-like enzymes, and the purpose of the present study was to examine whether any of five such enzymes, rK1, rK2, rK7, rK9 or rK10, can process the rat EGF precursor. Molecular weight forms of EGF, that were N- or C-terminally extended compared to submandibular gland EGF were obtained from rat urine. These extended forms of EGF were incubated with each of the enzymes for 24 h at 37 degrees C. Two enzymes, rK7 and rK10, were able to cleave N- and C-terminally extended EGF, releasing a form of EGF which eluted similarly to submandibular gland EGF upon gel filtration, and which was recognized both by antibodies against rat EGF and by the EGF receptor. One enzyme, rK1, cleaved C- but not N-terminally extended EGF. Neither rK2, nor rK9 cleaved the extended forms of EGF. In previous immunohistochemical studies rK1, rK7 and rK10 have all been demonstrated in the EGF containing cells of the rat submandibular gland. EGF and rK1 are also synthesized in the rat kidney but the present study demonstrated that EGF and rK1 are not colocalized in this organ. Based on the cleavage of the extended forms of rat EGF by rK1, rK7 and rK10 and on the fact that the enzymes are abundant and colocalized with EGF in the rat submandibular gland, we suggest that rK1, rK7 and rK10 can be involved in the processing of the EGF precursor in the rat submandibular gland.

Asynchronous reformation of individual kallikrein-related secretory proteinases in rat submandibular glands following degranulation by cyclocytidine

Time scales for the reformation of the secretory granules in granular tubules and their constituent proteinases were assessed after inducing a massive degranulation by intraperitoneal injection of cyclocytidine in conscious animals. The minimum working dose of cyclocytidine to produce the maximum degranulation and depletion of proteinase activity, at 3 h after injection, was 75 mg/kg. Histologically, although most granular tubule cells then appeared to be extensively degranulated, isolated individual cells showing little or no degranulation always persisted. Acinar cells also showed some depletion of secretory material. At 15 h after injecting cyclocytidine the formation of new granules had begun in the granular tubule cells, but it was not extensive or uniform in adjacent cells; however, the acinar cells already appeared to be regranulated. The pattern of granule reformation in granular tubule cells progressed gradually, so that 7-10 days after cyclocytidine-induced degranulation the cells were mostly packed with granules and showed similar appearances to those of normal resting control glands. Individual proteinases in extracts of the glands were assayed specifically using fluorogenic oligopeptide amidase substrates, with and without appropriate inhibitors. This revealed a 95% reduction in total proteinase activity 3 h after cyclocytidine (75 mg/kg). In the same extracts, acinar peroxidase was reduced by 28%. Peroxidase levels recovered to control values within 15 h after cyclocytidine but recovery of proteinases progressed more gradually and did not occur uniformly for the different constituent proteinases. Tissue kallikrein (rK1) showed the most rapid recovery and had reached levels approaching normal within 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of adrenergic agonists and antagonists on the expression of proteins in rat submandibular and parotid glands

The present investigation was undertaken to study the effect of adrenoreceptor modulators on the expression of salivary proteins. Sprague-Dawley rats were treated for 10 consecutive days with adrenergic agonists isoproterenol, dobutamine, terbutaline, salbutamol, methoxyphenamine, or methoxamine. Antiserum to selected salivary proteins was used to compare the concentration of these proteins in the submandibular and parotid glands of treated animals. Chronic treatments of rats (50 mumol/kg body weight for 10 d) with either isoproterenol or dobutamine induced synthesis of a cysteine-proteinase inhibitor (cystatin) in the submandibular glands. When isoproterenol was injected concomitantly with the mixed beta-antagonist propranolol or the beta 1-adrenergic antagonists metaprolol, protocol, or atenolol, the induction of cystatin was totally suppressed. However, the beta 2-antagonist, ICI-118551, produced only partial reduction in cystatin induction elicited by isoproterenol. On the contrary, rats treated with either isoproterenol or beta 1-agonists demonstrated a significantly reduced concentration of serine-proteinase kallikrein in submandibular glands. The decrease observed in submandibular kallikrein of rats treated with isoproterenol was prevented by concomitant treatment with beta 1-antagonists but not with beta 2-antagonists. Because kallikreins are produced by ductal cells and cystatins are produced by acinar cells of submandibular glands, these observations suggest that there may be differential control of expression of proteins synthesized by ductal and acinar cells. Chronic treatment of rats with nonselective beta-agonist isoproterenol or beta 1-selective agonists increased markedly the proline-rich proteins (PRP) in parotid glands, but the parotid amylase concentration was not significantly affected by beta-adrenergic agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Parotid secretion of fluid, amylase and kallikrein during reflex stimulation under normal conditions and after acute administration of autonomic blocking agents in man

The purpose of this work was to study the effect of graded mechanical and gustatory stimulation on the secretion of the acinar products fluid and amylase and the ductal product kallikrein from the human parotid gland (n = 9). The involvement of parasympathetic and sympathetic nerves in the salivary reflexes was subsequently examined using receptor blocking agents (n = 4). Chewing elevated the secretion of all products as compared to rest (P less than 0.013). When increasing the length of the chewing object, secretion of fluid (P less than 0.013), but not enzymes, further increased. The shift from mechanical to gustatory stimulation with 0.5% citric acid enhanced significantly the secretion of amylase and kallikrein (P less than 0.009), while application of 5.0% citric acid increased the secretion of both acinar products (P less than 0.009) more than kallikrein. A differentiated reflex control of salivation both with regard to input and output was thereby indicated. The muscarinic-cholinergic antagonist oxyphencyclimin reduced median fluid secretion between 54 and 76% depending on the stimuli. During citric acid stimulation, but not during chewing, fluid secretion was reduced about 40% by the beta 1-adrenergic antagonist metoprolol, and about 20% by the alpha 1-adrenergic antagonist prazosin. Median amylase secretion was reduced 30% during chewing and 75% during gustatory stimulation by metoprolol. It was concluded that the masticatory-salivary reflex mainly activated parasympathetic pathways producing saliva of low protein content.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of rat submandibular intralobular ducts

Intralobular (granular) salivary ducts were purified by isopycnic centrifugation after collagenase/hyaluronidase digestion of the rat submandibular gland. The resulting ductal fraction (density, 1.056 +/- 0.003) was highly enriched in kallikrein (a ductal cell marker) and contained little amylase activity (an acinar cell marker). The resting intracellular calcium level in the ductal preparation was 103 +/- 4 nM. Increased intracellular calcium concentrations (2-3 times resting levels) were observed in response to muscarinic (carbachol) and alpha-adrenergic (epinephrine) agonists, but little response was observed to substance P, suggesting the absence of substance P peptidergic receptors on rat submandibular ducts. Intracellular adenosine 3',5'-cyclic monophosphate levels were increased 35-fold in response to beta-adrenergic stimulation (isoproterenol) and forskolin. The ducts secreted kallikrein in response to epinephrine, carbachol, and isoproterenol but not in response to substance P. Epinephrine was the most potent inducer of kallikrein release with a K0.5 of approximately 3 microM and a maximal secretory rate approximately nine times unstimulated levels. Taken together, these results provide strong evidence for the functional integrity of the ductal preparation. This preparation should prove useful for the further elucidation of the properties of intralobular salivary ducts structures which heretofore have only been studied indirectly.

The effects of autonomic drugs on the concentration of kallikrein-like proteases and cysteine-proteinase inhibitor (cystatin) in rat whole saliva

The influence of isoproterenol, phenylephrine, propranolol, and reserpine on the salivary concentration of kallikrein-like proteases and cysteine-proteinase inhibitor (cystatin) was investigated. The protease activities in saliva from treated rats were studied by means of five different chromogenic substrates. In the isoproterenol- and phenylephrine-treated groups, a significant decrease in protease activity was found, compared with the control group. The protease activity of saliva was found to be elevated by about 25-50% after chronic administration of reserpine (0.5 mg/kg). Specific polyclonal antibodies to rat glandular kallikrein and cystatin were utilized to determine the salivary concentrations of these proteins. Results from the use of anti-kallikrein antibodies in Western blot analysis and crossed immuno-electrophoresis indicated that differences observed in the kallikrein-like protease levels of saliva from treated animals were due to altered immunoreactive protein levels. The salivary concentrations of kallikrein and cystatin were measured by direct radio-immunoassays with specific antibodies. The concentration of cystatin in the saliva of normal animals or animals treated with reserpine or propranolol was very low, but was increased about 100-fold in phenylephrine-treated animals and more than 5000-fold in isoproterenol-treated animals. Western blot analysis with antibodies to submandibular gland mucin, glutamine/glutamic-acid-rich protein (GRP), and proline-rich proteins (PRP) were also utilized to compare the effects of autonomic drugs on these salivary proteins. The salivary mucin showed an increase in reactivity and increased mobility in saliva from both isoproterenol- and phenylephrine-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Yohimbine increases submaxillary kallikrein release into the saliva in dogs: evidence for alpha 2-adrenoceptor-mediated inhibition of cholinergic pathways

1. The effects of the alpha 2-adrenoceptor antagonist, yohimbine (0.5 mg kg-1, i.v.) on basal, sympathetic and parasympathetic stimulation-induced submaxillary kallikrein release were investigated in the anaesthetized dog. Kallikrein was measured by its kininogenase activity before and after trypsin activation which also allowed a study of the proportion of active to total enzyme. 2. Yohimbine induced a rapid, three fold increase in basal kallikrein release correlated with an increase in salivary flow rate which lasted for 60 min following injection. 3. Sectioning the chorda tympani did not affect basal kallikrein release but abolished yohimbine-induced rise in salivary kallikrein secretion. 4. Parasympathetic stimulation alone induced a 3 to 4 fold increase in basal kallikrein release correlated with an increase in salivary flow rate. Yohimbine induced a significant additional increase in parasympathetic-stimulated kallikrein release. 5. When the cervical sympathetic nerve was sectioned the basal kallikrein release decreased by 30 to 40%. 6. Sympathetic stimulation alone also induced a 3 to 4 fold increase in basal kallikrein. This was not correlated with the salivary flow and unaffected by yohimbine. 7. The results indicate that yohimbine increases submaxillary kallikrein release into the saliva by inhibition of presynaptic alpha 2-adrenoceptors located on the chorda tympani nerve endings.

The effect of adrenergic agonists and antagonists on cysteine-proteinase inhibitor (cystatin) in rat saliva

The effect of a number of adrenergic agonists and antagonists on the induction of rat salivary cystatin was investigated. A highly sensitive and specific radioimmunoassay was used to determine cystatin in rat whole saliva. Treatment for 10 consecutive days with a non-specific beta-adrenergic agonist isoproterenol, or the beta 1-adrenergic agonists dobutamine or methoxyphenamine, resulted in the induction of the salivary cystatin. Induction was also found in rats treated for 10 days with arterenol. Only trace quantities of cystatin could be detected in saliva of rats treated with the beta 2-adrenergic agonists terbutaline or salbutamol. When isoproterenol was injected concomitantly with the mixed beta-antagonist propranolol or the beta 1-adrenergic antagonists metaprolol, proctocol or atenolol the production of cystatin was totally suppressed. However, the beta 2-antagonist, ICI 118551, produced only a partial reduction in salivary cystatin induction elicited by isoproterenol. The findings suggest that the induction of salivary cystatin is regulated, in part, by beta 1-adrenergic receptor stimulation.

Biologically active peptides in the gastrointestinal lumen

The release of a variety of biologically active peptides into the gastrointestinal lumen via gastric, duodenal and intestinal secretions, as well as in the saliva, pancreatic juice and bile, has been explored. The key features of luminal secretion of peptides such as secretion at high concentrations, neurohormonal regulation, luminal orientation of stimulated secretion, stability of peptides in the gastrointestinal lumen, altered secretion under pathophysiological conditions, and biological activity of luminally administered peptides are discussed. This review develops a detailed picture of the current understanding of luminal secretion of peptides and their possible biological functions under normal and pathophysiological conditions.

Exocrine and endocrine release of kallikrein after reflex-induced salivary secretion

Exocrine and endocrine release of rat submandibular gland kallikrein has been shown to be low after parasympathetic and beta-adrenergic stimulation but greatly increased after alpha-adrenergic stimulation. In the present study, release of glandular kallikrein was investigated under conditions known to give a reflex-induced salivary gland response. Heat stress induced a rich flow of saliva originating in the submandibular glands. Salivary kallikrein secretory rate was higher than after parasympathetic stimulation but lower than after sympathetic stimulation (P less than 0.005). Only heat stress increased circulating glandular kallikrein (12.7 +/- 0.8 ng ml-1 before heat exposure and 53.3 +/- 14.1 ng ml-1 40 min afterwards, P less than 0.005). There were no indications that the endocrine release of kallikrein was due to non-specific leakage. Atropine abolished heat-induced salivation and endocrine kallikrein secretion, possibly through interference with central pathways (P less than 0.05). However, phentolamine did not, which may indicate as an yet unidentified mediator of endogenous kallikrein release. The salivary gland response to acid and ether was comparable to that observed after parasympathetic nerve stimulation and was abolished by atropine (P less than 0.005). Stimuli known to influence other salivary gland ductal cells, such as aggression and starvation followed by drinking, also did not increase the plasma concentration of glandular kallikrein. The fact that various conditions which induce salivation did not increase circulating glandular kallikrein, coupled with the fact that kallikrein concentration was the highest in animals that died from heat stress, may suggest that the increase in circulating glandular kallikrein seen after heat stress may be pathological and could contribute to the development of heat shock.

The role of chemical mediators in the pathogenesis of inflammation with emphasis on the kinin system

In recent years, numerous agents have been recognized as inflammatory mediators. In this review, however, we discuss only those having direct relevance to human inflammatory diseases These mediators are clinically important due to their proinflammatory properties such as vasodilatation, increased vascular permeability, pain and chemotaxis. They may lead to the fifth cardinal sign, loss of function in inflammatory diseases. Agonists and non-specific antagonists are used as pharmacological tools to investigate the inflammatory role of PGs, LTs, PAF, IL-1, histamine, complement, SP, PMN-leukocytes, and kallikrein-kininogen-kinin systems. Unfortunately, no compound is known which concurrently abolishes all actions and interactions of inflammatory mediators. Therefore it would be highly useful to promote efforts in developing selective and competitive antagonists against proinflammatory actions of these chemical mediators. This may help to a better understanding of the pathogenesis of inflammatory reactions, and it may also be useful for the therapy of inflammatory diseases.

Secretory character of a group of isoproterenol-induced polypeptides in mouse parotid glands

The secretory nature of the isoproterenol-induced mouse parotid polypeptides C, D, E, F, and G (molecular weights 64,000, 61,000, 51,500, 38,000, and 37,000, respectively) is documented. Polypeptides C, D, E, F, and G, accumulated in response to successive daily stimulations with isoproterenol, were detected in a fraction enriched in hypertrophic parotid acinar cells. These cells, characterized by an increased content of cytoplasmic granules, maintain a secretory responsiveness to isoproterenol, which has been evidenced by light microscopy, enzymatic analysis, and unidimensional SDS-polyacrylamide gel electrophoresis. Thus, a parallelism in the loss and recovery of both secretory granules, alpha-amylase and polypeptides C, D, E, F, and G, was observed. Moreover, after secretion stimulation, polypeptides C, D, E, F, and G were detected in the fluid collected directly from parotid gland cannulation. Given the secretory character of polypeptides C, D, E, F, and G, mechanisms explaining both their progressive accumulation along the chronic administration of isoproterenol, as well as their progressive disappearance observed after suspending that treatment, are discussed.

Interrelationship between the kallikrein-kinin system and hypertension: a review

The evidence presented here suggests strongly that the kallikreins-kininogens-kinins-kininase II system has most significant role in regulation of systemic BP. This system is involved in mediation and modulation of renin-angiotensin-aldosterone, PGS and vasopressin in the regulation of sodium water balance, renal hemodynamic and BP. Therefore, reduction in the kinin-formation due to high production of kininase II, and lower formation of tissue kallikrein might result in an increased release of vasoconstrictor angiotensin II on one side, and on the other side much reduced production of PGE, vasodilator. These changes might lead to deranged vascular smooth muscle structures and cell membrane functions, retention of sodium and water, increased plasma volume, and renovascular constriction. These physiological defects might result in the development of essential hypertension (Fig. 4). Although, it is possible now to treat hypertensive conditions with tissue kallikrein and kininase II inhibitors. These discoveries have opened up new vistas to research on the pharmacological applications of kallikreins-kininogens-kinins-kininases in human diseases.

Rat urinary kallikrein localization in kidney: effects of fixation

The influence of fixation on the immunocytochemical localization of tissue kallikrein in the kidney has been evaluated using both monoclonal and polyclonal antibodies. These studies have provided several results relevant to kallikrein localization in kidney: (1) the intensity and distribution of immunostaining with both polyclonal and monoclonal anti-kallikrein antibodies is fixation-dependent; (2) the most intense and consistent localizations of kallikrein are in the connecting tubule and the cortical collecting duct of the nephron; (3) kallikrein-like immunoreactivity is seen in proximal tubules with polyclonal but not with non-cross-reactive monoclonal antibodies; and (4) fixatives which disrupt membranes reveal a kallikrein-like antigen in straight tubules of the outer medulla. However, immunostaining with monoclonal antibodies indicates that much of the observed immunostaining at this site probably represents cross-reactivity with another member of the kallikrein family of enzymes.

Effect of autonomic nerve stimulation on bleb formation in striated duct cells of the rat submandibular gland

Several previous investigations have shown that blebs form on the apical surface of the striated duct cells of the rat submandibular gland on feeding after starvation. In the present report the influence of autonomic nerve stimulation on bleb formation was studied by electron microscopy. Both parasympathetic and sympathetic stimulation were performed, using electric nerve stimulation. In addition, sympathetic nerve stimulation in combination with alpha- or beta-adrenergic blockers was used. Massive bleb formation took place in response to sympathetic nerve stimulation. This response was almost completely abolished by the administration of alpha- but not by beta-adrenergic blocker. Bleb formation was not seen after parasympathetic nerve stimulation.

Ultrastructure of the secretory response of male mouse submandibular gland granular tubules

The organization and fine structure of granular convoluted tubule cells (GCT) from male mouse submandibular glands have been examined in controls and in animals injected with adrenergic and cholinergic secretagogues. Control submandibular glands exhibited a single population of GCT cells with numerous homogeneous granules filling the apical two-thirds of the cytoplasm. A zone of transition cells, exhibiting characteristics of both GCT and striated duct cells, was found between the agranular intercalated duct and GCT segments. These transition cells possessed apical granules of variable size as well as prominent basal striations. Dramatic changes in the morphology of GCT cells followed administration of the alpha-adrenergic agent, phenylephrine. The extensive degranulation involved formation of "secretory pools" of fused granules and release of secretory material into the lumen. The appearance of numerous smooth vesicles near luminal membranes suggested extensive membrane retrieval. Intracellular membrane-limited aggregates of membrane fragments suggested that much of the retrieved membrane was destined for degradation. Rough endoplasmic reticulum was highly dilated but there was no indication of increased size or activity of the Golgi complex. Ultrastructural evidence indicated that the secretory responses to isoproterenol, a beta-adrenergic agent, and to pilocarpine, a cholinergic agent, were much more modest, but it is clear that some secretory response to these agents does occur. The other cell types of the duct and tubule system did not exhibit comparable morphological changes in response to the agents used.

Role of calcium and calmodulin in release of kallikrein and tonin from rat submandibular gland

We investigated the role of calcium and calmodulin as intracellular mediators of kallikrein and tonin release induced by norepinephrine (NE). We studied the secretion rate of kallikrein and tonin from submandibular gland of rat in response to NE in the presence or absence of calcium, two calcium blockers, and four different calmodulin antagonists. Submandibular gland slices were incubated in vitro, and glandular kallikrein and tonin secreted into the incubation medium were determined by direct radioimmunoassays and expressed as nanograms per minute per milligram tissue. NE (10(-5) and 10(-4) M) increased the kallikrein secretion from the control value of 8.2 +/- 2.6 to 134.9 +/- 41.4 (P less than 0.05) and to 191.2 +/- 62.7 (P less than 0.05), and the release of tonin from a basal rate of 3.5 +/- 0.6 to 51.5 +/- 9.1 (P less than 0.05) and to 64.4 +/- 13.7 (P less than 0.05). The deletion of calcium and addition of EGTA into the incubation medium significantly attenuated the secretion of kallikrein and tonin induced by NE. Nifedipine, at concentrations which inhibit voltage-dependent calcium channels, did not affect the release of kallikrein and tonin, and only a high concentration (10(-4) M) reduced the release. TMB-8, a blocker of intracellular calcium, had no effect either. Phenothiazines, triflupromazine (10(-6) M) and trifluoperazine (10(-4) M), decreased significantly the kallikrein release elicited by 10(-5) M NE.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of kallikrein and tonin from the rat submandibular gland

The interaction of neurotransmitters and hormones with specific receptors on the plasma membranes of cells results in enzyme secretion from exocrine glands. However, the effects of agonists on the release of kallikrein and tonin from the rat submandibular gland have not yet been evaluated systematically. The purpose of the present study was to investigate the effects of norepinephrine, isoproterenol, methacholine, and cholecystokinin on the simultaneous release of kallikrein and tonin from the rat submandibular gland. Submandibular gland slices were incubated in vitro at 37 degrees C in a modified Krebs-Ringer medium containing 0.2% each of glucose and bovine serum albumin and bubbled with a gas mixture of 95% O2 and 5% CO2. Glandular kallikrein and tonin secreted into the incubation medium were determined by specific radioimmunoassays. Norepinephrine at 10(-5) M concentration increased kallikrein secretion from a control value of 7.7 +/- 1.5 to 114.7 +/- 26.9 ng/min/mg tissues (p less than .01), and at 10(-4) M concentration kallikrein secretion increased to 265.9 +/- 58.3 ng/min/mg tissue (p less than .01). Similarly, norepinephrine at 10(-5) M enhanced the release of tonin from a basal rate of 4.4 +/- 0.6 to 57 +/- 14.4 ng/min/mg tissue (p less than .05), and at 10(-4) M the rate increased to 91.3 +/- 20.0 ng/min/mg tissue (p less than .01). In contrast, isoproterenol, methacholine, and cholecystokinin did not increase the secretion of kallikrein or tonin. We conclude that the secretion of kallikrein and tonin from rat submandibular glands upon sympathetic stimulation is mediated through stimulation of alpha-adrenoceptors only.

Effects of a phorbol ester and diacylglycerols on secretion of mucin and arginine esterase by rat submandibular gland cells

The effects of a phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and a diacylglyceride, 1-oleoyl-2-acetyl-glycerol (OAG) on the secretion of two major exocrine products by dispersed rat submandibular cells were investigated. TPA stimulated the release of acinar cell mucin and ductal cell protease (arginine esterase) in a dose- and time-dependent manner. Mucin secretion was also provoked by OAG, which, however, had no effect on arginine esterase release. The unsaturated diacylglycerol, 1,2-diolein, elicited a greater mucosecretory response than did OAG at the same concentration, while the saturated 1,2-distearin produced a smaller response. Mucin and enzyme secretion caused by TPA or OAG in the rat submandibular model was not inhibited by either of two putative antagonists, the antipsychotic drug, fluphenazine, and the antibiotic, polymyxin B. The involvement of extracellular Ca2+ in TPA-induced secretion was examined by comparing responses of cells maintained in normal or Ca2+-free medium, or in medium containing the ionophore A23187. Although extracellular Ca2+ was not an absolute requirement for a secretory response, the results indicate a synergistic relationship between TPA and Ca2+ in stimulating the release of both mucin and arginine esterase. These results suggest a role for the Ca2+-, phospholipid-dependent enzyme, protein kinase C in the secretory mechanism of mucous and serous cells in the submandibular gland. This is consistent with the proposal that receptor-mediated hydrolysis of membrane phosphoinositides is an initial event in stimulus-response coupling in exocrine cells.

Kallikrein excretion in renal transplant recipients and in uninephrectomized donors

The rate of tissue kallikrein (EC 3.4.21.35) excretion into the urine has been examined with an active site-specific radioimmunoassay for kallikrein in renal transplant recipients, in post-uninephrectomy kidney donors, and in a normal control population. Normal individuals on uncontrolled diets excreted 96.88 +/- 7.00 (SEM) micrograms of active kallikrein/24 hr and 113.68 +/- 8.39 micrograms of total kallikrein/24 hr, as determined after trypsin treatment of urine samples. Uninephrectomized donors secreted significantly less (P less than 0.05) active (44.99 +/- 6.39 micrograms/24 hr) and total (73.59 +/- 11.95 micrograms/24 hr) kallikrein than either the entire normal population or an age-matched subpopulation. Recipients with good renal function who had received kidneys 2 to 13 years prior to kallikrein assay excreted less (P less than 0.05) active (13.21 +/- 2.50 micrograms/24 hr) and total (18.69 +/- 3.65 micrograms/24 hr) kallikrein than either normal or uninephrectomized populations. Similar values for active (11.05 +/- 1.56 micrograms/24 hr) and total (17.60 +/- 1.96 micrograms/24 hr) kallikrein were seen in patients who had received kidneys within 6 months of assay. Thus, kallikrein excretion in kidney recipients remains significantly lower than in uninephrectomized donors. As compared to normal individuals, the reduced kallikrein excretion in post-uninephrectomized kidney donors and in renal allograft recipients suggests that renal kallikrein excretion may reflect functional distal tubular mass.

The renal kallikrein-kinin system in spontaneously hypertensive rats

In male spontaneously hypertensive rats (SHRSP) of the stroke prone strain (Okamoto) and in normotensive Wistar-Kyoto rats (WKY) urinary kallikrein excretion was investigated at different age and at drug-induced diuresis. In rats of both strains from 7th till 19th week of age urinary kallikrein excretion increased with age. In SHRSP of 7th till 11th week of age kallikrein excretion was higher than in WKY rats, while it was lower in the 48-week-old SHRSP. No correlation was found between urinary kallikrein excretion and systolic blood pressure. In SHRSP and WKY rats a similar daily rhythm of kallikrein excretion in urine was found being high in the early morning and low in the afternoon. Kallikrein excretion correlated significantly with urine volume. The loop diuretic bumetanide (4 and 40 mg/kg) induced diuresis and natriuresis in both strains, however more marked in the WKY rats than in the SHRSP. Urinary kallikrein excretion, however, showed in both strains the same biphasic course with a short lasting increase and a secondary decrease. Thus, in the average urinary kallikrein excretion was not effected by the drug. Prolonged treatment with furosemide over 5 days (125 mg/kg) resulted in an increase in kallikrein excretion in urine, more pronounced in the WKY rats than in the SHRSP. The observed results suggest that renal kallikrein-kinin system is not involved in the development of spontaneous hypertension as a pathogenetic factor, but rather is influenced by other factors like hormone interactions, i.e. mineralocorticoids and catecholamines, as well as renal function and acute changes in urine flow.

Effect of substance P on exocrine secretion by rat submandibular gland cells

The effects of the undecapeptide, substance P(SP), on the secretion of mucin and proteolytic enzymes from dispersed cells of the rat submandibular gland were studied. The peptide, at a concentration of 1 X 10(-7) M, stimulated the release of 31.9 +/- 3.0% (mean +/- SEM) of intracellular mucin over 40 min, compared with 12.5 +/- 1.5% in untreated controls (p less than 0.01). This effect was duplicated by the homologous peptides, physalaemin, and eledoisin-related peptide. Substance P action was not affected by pre-incubation of cells with phentolamine or propranolol and was therefore independent of adrenergic stimulation. Furthermore, SP did not enhance the intracellular concentrations of cyclic AMP or cyclic GMP, confirming that cyclic nucleotides were not involved in its stimulus-secretion coupling mechanism. The isoproterenol-stimulated secretion of mucin from dispersed cells was reduced to 75.7% of the normal response (p less than 0.01) after a brief exposure to SP. This inhibitory effect was probably mediated by intracellular events rather than by direct effects on cell surface receptors. However, mucin release after treatment with SP followed by norepinephrine (NE) was 161% of that caused by NE alone (p less than 0.01) and may reflect an additive response to the independent stimulation of SP and NE receptors. Substance P and related peptides had no effect on arginine esterase secretion in the experimental model, although a response was elicited by alpha- and beta-adrenergic agonists. It is, therefore, proposed that serous cells of the granular convoluted tubule in the rat submandibular gland lack substance P receptors.

Release of kallikrein-like esterase and tonin from dispersed cells of the rat submandibular gland

Viable dispersed cell preparations of rat submandibular gland were obtained by a tissue-dissociation procedure using collagenase and gentle mechanical force. The cells released kallikrein-like esterase in a time- and calcium-dependent manner in response to noradrenaline (10 microM) at 30 degrees C. The net loss of kallikrein-like esterase content from the dispersed cells corresponded with the increase in kallikrein-like esterase activity in the suspending medium at all concentrations of noradrenaline. These results indicate the viability and functional integrity of this dispersed cell preparation of rat submandibular gland. alpha-Adrenoceptor agonists such as noradrenaline stimulated kallikrein-like esterase and tonin release in a dose-dependent manner, whereas the beta-adrenoceptor agonist isoprenaline and cholinoceptor agonist methacoline were both inactive. Noradrenaline-induced release of kallikrein-like esterase and tonin were completely blocked by prior addition of the alpha-adrenoceptor antagonist, phenoxybenzamine. It is concluded that the secretion of kallikrein-like esterase and tonin in rat submandibular gland is mediated only via stimulation of alpha-adrenoceptors.

Immunohistochemistry of tonin in rat submandibular gland during development, lactation and secretion

Tonin is a serine protease found in high concentrations in the submandibular gland (SMG) of the adult rat where it has been localized by immunohistochemistry in the granular ducts. The present study examined the development of tonin in the SMG, the effect of lactation and of stimulation of tonin release, using the peroxidase-antiperoxidase technique and antitonin. Tonin-like immunoreactivity first appeared in the primitive striated duct of the SMG on day 19 foetal and increased in intensity as the ducts developed into granular ducts. Reaction product in granules was seen on day 17 postpartum. Its localization within granules was established by immunochemistry of Sepharose beads to which had been coupled the contents of granules isolated from adult rats. The granular ducts of female rats, which are less developed than in the male, showed a marked increase in tonin-immunoreactivity during lactation. Stimulation of tonin secretion by isoprenaline caused massive discharge of tonin-like immunoreactivity into the lumen of the granular ducts during in vitro incubation. However, within one hour complete regranulation was apparent. The secretion was prevented by propranolol. The results indicate that tonin or a tonin-like substance appears in the rat submandibular gland late in gestation in ducts that presumably develop into granular ducts where it is found in abundance in granules in the adult, that the amount in females is increased during lactation, and that most of the granules are discharged during stimulation, only to be rapidly replaced.

Role of the autonomic nervous system in the release of rat submandibular gland kallikrein into the circulation

We have previously demonstrated that the rat submandibular gland releases immunoreactive kallikrein into the circulation. To study the role of the autonomic nervous system in this release, submandibular gland blood flow and kallikrein concentration in peripheral arterial and venous blood from the gland were measured and secretion rates calculated before and after parasympathetic and sympathetic nerve stimulation (8V, 2 msec, 10 Hz) for 1 minute. Immunoreactive kallikrein in plasma was measured by radioimmunoassay, and timed collections of venous outflow were used to measure blood flow. During basal conditions, the unstimulated submandibular gland of the rat released immunoreactive kallikrein into blood at the rate of 0.92 +/- 0.07 ng/min. Parasympathetic stimulation increased blood flow 4-fold (before, 68.5 +/- 8.3 microliters/min; after, 253.5 +/- 76.2; P less than 0.05) without significantly changing immunoreactive kallikrein secretion rate. Sympathetic stimulation produced an 11-fold increase in blood flow (before, 64.9 +/- 9.3 microliters/min; after, 709.6 +/- 97.5; P less than 0.05) and a 57-fold increase in immunoreactive kallikrein secretion rate from the gland (before, 1.05 +/- 0.25 ng/min; after, 59.8 +/- 18.6; P less than 0.05). Sympathetic stimulation also produced a 4-fold increase in the concentration of immunoreactive glandular kallikrein in arterial plasma (before, 15.2 +/- 1.1 ng/ml; after, 56.2 +/- 12.9; P less than 0.05). Pretreatment with phentolamine (1 mg/kg) or prazosin (0.2 mg/kg) blocked the increase in kallikrein secretion rate produced by sympathetic stimulation. These results indicate that the sympathetic nervous system, through activation of alpha 1-adrenoreceptors, controls kallikrein secretion from the submandibular gland into the circulation. Released kallikrein may be responsible for the reactive vasodilation observed in the rat submandibular gland after sympathetic stimulation.

Excess antibody immunoassays for rat glandular kallikreins. Measurement of kallikrein from different organs in the presence of cross-reacting antigens

An immunoradiometric assay has previously been developed for measurement of rat glandular kallikrein. In the present paper, further studies on the specificity and sensitivity of the method are described. Problems of interference of immunologically cross-reacting antigens were overcome by proper preabsorption of the antibody. A method was thus established in which enzymatic activity of the immunoreactive kallikrein could be measured even in the presence of enzymes sharing immunological determinants and substrate specificity with kallikrein. Two variants of the immunoradiometric assay have been evaluated. A simplified version with simultaneous addition of all reagents gave results equal to those obtained in the original assay. A further modification with delayed addition of the solid-phase antibody, gave considerable improvement in assay sensitivity.

Radioimmunoassay of rat submandibular salivary gland mucin

A solid phase radioimmunoassay (RIA) for rat submandibular mucin (RSM) was developed and applied to studies of mucin concentration, antigenicity and secretion. The assay utilizes the affinity of 125I-Protein A for IgG to quantitate antigen-antibody immunocomplexes immobilized in the wells of plastic microtitre plates. The technique was highly reproducible and capable of detecting as little as 3 ng mucin protein. The submandibular glands of rats weighing 150-180 g contained 257 micrograms of mucin (dry wt) per mg protein, which is equivalent to about 3.6 mg of mucin per gland. The antiserum to RSM was cross-reactive with mucins from rat sublingual and pig submandibular glands, and rat, human and pig small intestine. No cross-reactivity was detected with mucins from mouse, canine or bovine submandibular glands, and there was no evidence that ABH blood-group sugars contributed to mucin antigenicity. The RIA was used to estimate secretion from dispersed rat submandibular gland cells and gave a more specific and accurate assay of mucin release than previous assays of precursor-labelled radioactive glycoproteins in the culture medium. The beta-adrenergic agonist, isoproterenol, stimulated immunoreactive mucin secretion from cultured cells to approximately twice the level of unstimulated or propranolol-inhibited controls. The RIA appears to offer promising new approaches for studies on mucin metabolism and secretion in health and disease.

In-vivo effects of prostaglandin E1 and lysine-bradykinin on rat salivary secretions elicited by parasympathomimetic stimulation

Intravenous injections of either prostaglandin E1 or lysine bradykinin (kallidin) modified the secretory response of the submandibular, parotid and sublingual glands of the rat to intravenous infusions of acetylcholine. The two substances caused reductions (of from 16 to 67 per cent) in salivary flow rates when administered in concentrations ranging from 10 to 50 micrograms/kg body weight. The effect lasted for 20-30 min, followed by a return to pre-injection levels and in general, depended on the concentration of the secretory stimulator and on the dose of test substance used. In the submandibular and sublingual gland, both substances generally caused a concomitant increase in the salivary Na+ concentrations. This effect depended on the concentrations of acetylcholine and of test substance and varied from 10 to 117 per cent. The effect was more marked in submandibular saliva. Absolute increases in salivary Na+ concentration were not observed in the parotid gland, but the reductions in salivary Na+ concentrations (from 2.5 to 31.7 per cent) were smaller and did not parallel the simultaneous reduction in flow rate, which was between 16.4 and 60.4 per cent. As both kinins and prostaglandins are present in the glands and may be activated as a result of secretory or metabolic activity, the results suggest that they act as modulators of the secretory response to cholinergic stimulation. The divergent effects on flow rate and on salivary Na+ concentration suggest that kinins and prostaglandins have specific and independent effects on acinar and duct cells.

Clonidine decreases rat urine kallikrein excretion by alpha-adrenergic receptor stimulation

In normal conscious female Sprague-Dawley rats, clonidine dose-dependently (10-300 micrograms/kg) decreased urine kallikrein excretion to approximately 40% of the control value. The effect of clonidine on urine enzyme excretion was inversely related to diuresis-natriuresis. Phenoxybenzamine (1 mg/kg) or phentolamine (10 mg/kg) antagonized the effect of clonidine on urine enzyme excretion. Consequently, rat urine kallikrein excretion might be reduced when alpha-adrenergic receptors are stimulated by clonidine.

Nerve growth factor and an anticomplimentary protease in mouse saliva elicited by nerve stimulation

1. Three substances previously identified in mouse saliva ((1) biologically active nerve growth factor (NGF), (2) a material immunologically identical to the alpha-subunit of 7S-NGF and (3) an anticomplementary protease) were quantified in both mandibular gland saliva and mixed salivary secretions elicited by stimulation of either the sympathetic or parasympathetic nerves to the salivary glands. 2. The concentrations and specific activities of all three substances in pure mandibular saliva equalled or exceeded those found in mixed secretions from all salivary glands. 3. All three substances were found to be primarily secreted as a result of sympathetic rather than parasympathetic nerve stimulation as their concentrations and specific activities were much greater in sympathetic than in parasympathetic mixed salivary secretions. 4. Bioactive NGF, alpha-subunit-like material, and an anticomplementary protease were demonstrated to be released selectively through activation of alpha-adrenergic receptors as the concentrations and specific activities of all three substances were markedly reduced by pre-treatment with an alpha-adrenergic blocker (phenoxybenzamine) but not by pre-treatment with either a muscarinic or a beta-adrenergic blocker (atropine or propranolol, respectively). 5. Measurement of total protein in saliva elicited by sympathetic nerve stimulation following pre-treatment with an alpha-adrenergic, beta-adrenergic, or muscarinic blocking agent demonstrated that proteins other than those examined in the present study must be released by activation of beta-adrenergic receptors.