Methacholine-induced Secretion Research Articles

Hypertonic saline increases secretory and exudative responsiveness of human nasal airway in vivo.

Hypertonic saline (HS) is used in sputum induction studies. However, little is known about the physiological effects of HS on human airways in vivo. The present study takes advantage of the fact that the airway effects of topical challenges may be accurately examined in the readily accessible nasal airway. The present study specifically examines whether exposure to HS affects histamine challenge-induced exudation of plasma (alpha2-macroglobulin) and methacholine-induced secretion of mucin (fucose). Isotonic saline and HS (27 and 45 g x L(-1)), with and without concomitant histamine challenges, and with and without preceding methacholine challenges, were administered onto the nasal mucosa in 16 healthy subjects. Lavage fluid levels of alpha2-macroglobulin and fucose were analysed. Histamine produced a significant mucosal output of plasma (alpha2-macroglobulin). HS itself did not evoke exudation of alpha2-macroglobulin, but it significantly increased the plasma exudation effect of histamine. Methacholine produced a significant nasal mucosal output of fucose. HS also increased the mucin secretion (fucose), and it enhanced the secretory effect of methacholine. The authors concluded that hypertonic saline alone evokes mucinous secretion in human nasal airways in vivo and that it also enhances the exudative and secretory effects of histamine and methacholine, respectively. Through different mechanisms the HS exposure may also improve the recovery of soluble indices in human nasal airways. Whether or not the present findings are translatable to human bronchial airways remains to be examined.

Early radiation effects on muscarinic receptor-induced secretory responsiveness of the parotid gland in the freely moving rat.

Although the salivary glands have a low rate of cell turnover, they are relatively radiosensitive. To study the possible mechanism behind this inherent radiosensitivity, a rat model was developed in which saliva can be collected after local irradiation of the parotid gland without the use of anesthetics or stressful handling. Saliva secretion was induced by the partial muscarinic receptor agonist pilocarpine (0.03-3 mg/kg) with or without pretreatment with the beta-adrenoceptor antagonist propranolol (2.5 mg/kg), or the full muscarinic receptor agonist methacholine (0.16-16 mg/min), and measured during 5 min per drug dose before and 1, 3, 6 and 10 days after irradiation. The maximal secretory response induced by pilocarpine plus propranolol was increased compared to that with pilocarpine alone but did not reach the level of methacholine-induced secretion, which was about five times higher. One day after irradiation a decrease in maximal pilocarpine-induced secretion was observed (-22%) using the same dose of pilocarpine that induces 50% of the maximal response (ED(50)), in both the absence and presence of propranolol, indicating that the receptor-drug interaction was not affected by the radiation at this time. The secretory response to methacholine 1 day after irradiation, however, was normal. At day 3 after irradiation, the maximal methacholine-induced secretion was also affected, whereas pilocarpine (+/-propranolol)-induced maximal secretion decreased further. At day 6 after irradiation, maximal secretory responses had declined to approximately 50% regardless of the agonist used, whereas ED(50) values were still unaffected. No net acinar cell loss was observed within the first 10 days after irradiation, and this therefore could not account for the loss in function. The results indicate that radiation does not affect cell number or receptor-drug interaction, but rather signal transduction, which eventually leads to the impaired response. We hypothesize that the early radiation effect, within 3 days, may be membrane damage affecting the receptor-G-protein signaltransfer. Later critical damage, however, is probably of a different nature and may be located in the second-messenger signal transduction pathway downstream from the G protein, not necessarily involving cellular membranes.

Anticholinergic properties of brompheniramine, chlorpheniramine, and atropine in human nasal mucosa in vitro.

Brompheniramine and chlorpheniramine have anticholinergic activities, but the relative potency of these effects has not been well defined. The anticholinergic properties of brompheniramine, chlorpheniramine, and atropine were assessed in an in vitro model of human nasal mucosal glandular secretion. Methacholine was used as a cholinergic agonist to stimulate glandular secretion of 7F10-mucin. These drugs (0.01-1000 microM) or vehicle (saline) were added to explant cultures with and without 100 microM methacholine. 7F10-mucin concentrations were measured in culture supernatants after 2-hour incubations. The effective dose reducing methacholine-induced secretion (ED50) was determined. ED50 was 0.25 microM for atropine, 4.10 microM for brompheniramine, and 4.63 microM for chlorpheniramine. None of the anticholinergic drugs changed spontaneous glandular exocytosis. Brompheniramine and chlorpheniramine are equipotent anticholinergic agents in human nasal mucosa in vitro. Atropine was 16 to 19 times more potent.

YM022, a potent and selective gastrin/CCK-B receptor antagonist, inhibits peptone meal-induced gastric acid secretion in Heidenhain pouch dogs.

We examined the affinity of YM022, a potent and selective gastrin/CCK-B receptor antagonist, for canine gastrin/CCK-B and CCK-A receptors and the effects of YM022 on secretagogue- and peptone meal-induced acid secretion in the denervated, surgically separated (Heidenhain) canine gastric pouch model in comparison with those of famotidine, an H2-receptor antagonist, and atropine. YM022 inhibited the binding of [(125)I]CCK-8 and [(3)H]devazepide to canine gastrin/CCK-B and CCK-A receptors, with IC50 values of 0.73 and 136 nM, respectively. Intravenous YM022 dose-dependently inhibited pentagastrin- and peptone meal-induced acid secretion with ED50 values of 0.0261 and 0.0654 micromol/kg, respectively, without affecting histamine- or methacholine-induced acid secretion. Famotidine inhibited acid secretion induced by all stimulants, while atropine inhibited the acid secretion induced by every stimulant except histamine. These results indicated that YM022 is a highly potent and selective antagonist for the canine gastrin/CCK-B receptor and suppressed pentagastrin- and peptone meal-induced gastric acid secretion without affecting histamine- or methacholine-induced acid secretion in Heidenhain pouch dogs.

Human nasal mucosal neutral endopeptidase (NEP): location, quantitation, and secretion.

Neutral endopeptidase (E.C.3.4.24.11, enkephalinase, NEP) is a potentially important enzyme capable of regulating the activity of neuropeptides released in the respiratory mucosa. In order to confirm the existence of NEP in the human respiratory mucosa, inferior nasal turbinate mucosae obtained at surgery and nasal secretions induced by topical provocations with methacholine, histamine, and allergen were analyzed for: (1) NEP activity (pmol product/min/ml) by enzymatic degradation of [3H]leu-enkephalin, (2) the presence of NEP-immunoreactive material by Western blot analysis, and (3) cellular localization of NEP distribution by immunohistochemistry. NEP activity in human nasal secretions obtained after normal saline challenge was 0.15 +/- 0.06 pmol/min/ml. Secretion increased to 0.86 +/- 0.26 pmol/min/ml after methacholine provocation and 1.69 +/- 0.74 pmol/min/ml after histamine provocation. The increase in NEP activity in methacholine-induced secretions was prevented by atropine (0.13 +/- 0.06 pmol/min/ml). After methacholine, histamine, and antigen nasal provocation, the kinetics of NEP appearance correlated more closely to the glandular marker, lactoferrin, than with the vascular markers albumin and IgG. In homogenates of nasal mucosa, the membrane fraction contained significantly more NEP on a per mg protein basis than did the soluble fraction (227.6 +/- 50.52 versus 9.61 +/- 3.18 pmol/min/mg protein, respectively, P < 0.01, n = 6). NEP in the membrane fraction was detected as a single band migrating at 97 kD on Western blots using antibodies specific for NEP and the common acute lymphoblastic leukemia antigen (CALLA). Immunoreactive NEP was localized to serous cells of the submucosal glands, epithelial cells, and endothelial and myoepithelial cells of small vessels. Staining for NEP in the serous cells was of the same intensity as that in epithelial cells. These results indicate that 97 kD NEP-immunoreactive material exists in discrete locations in the nasal mucosa, including the epithelium, serous cells of the submucosal glands, and vessel walls, and that NEP activity is detected as a minor component in nasal secretions enriched by glandular products. In addition to the modulating functions of NEP on neuropeptide-mediated activities on vessels and glands, it is possible that NEP in secretions plays a role in regulating mucosal responses to luminal neuropeptides or other as yet uncharacterized NEP substrates.

Muscarinic receptor subtypes in human nasal mucosa: characterization, autoradiographic localization, and function in vitro.

Muscarinic receptors play important roles in the regulation of glandular secretion and vasomotor tone in human nasal mucosa. M1, M2, and M3 muscarinic receptor subtypes were pharmacologically characterized in human inferior turbinates by receptor-binding assays using [3H](-)quinuclidinyl benzilate (QNB, identifies total muscarinic receptors) and [3H]-pirenzepine (PZ). Receptors were localized by autoradiography, and their function examined in vitro by assaying mucus secretion from cultured nasal mucosal explants. In competition assays, PZ was employed as a selective muscarinic antagonist for M1 receptors, gallamine and AF-DX 116 for M2 receptors, and 4-DAMP for M3 receptors. These ligands are selective at low nanomolar concentrations, but can interact with other muscarinic receptors at higher concentrations. It is not known if they can interact with putative M4 and M5 muscarinic receptor subtypes. Using [3H](-)QNB, total muscarinic receptor binding was 688.4 +/- 49.6 fmol/mg protein (Bmax), with a Kd of 1.47 +/- 0.13 nM. [3H]-PZ bound to 45% of the total QNB binding sites. In competition experiments, 4-DAMP displaced [3H](-)QNB with the lowest IC50, followed by PZ and AF-DX 116. Autoradiograms demonstrated that [3H](-)QNB binding was completely displaced by 4-DAMP, partially displaced by PZ, but not displaced by gallamine or AF-DX 116, and suggested that M1 and M3 subtypes coexist in submucosal glands. The localization of M1 receptors on submucosal glands was confirmed by direct labeling with [3H]-PZ. [3H]-PZ also labeled vessels, but with a low silver grain density. Autoradiographic [3H]-QNB binding was displaced by 4-DAMP and atropine, but not by PZ, gallamine, or AF-DX 116. In studies of mucus secretion in vitro, 4-DAMP significantly inhibited methacholine-induced secretion. Although less effective, PZ also had significant inhibitory effects. Neither gallamine nor AF-DX 116 had any inhibitory effect. M1 receptors (PZ binding sites) may regulate glandular secretion while M3 receptors (4-DAMP binding sites) may regulate glandular secretion and vasomotor tone in human nasal mucosa.

Role of thapsigargin-sensitive intracellular Ca2+ pools in secretion induced by muscarinic agonists in porcine adrenal chromaffin cells.

The role of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]-sensitive Ca2+ pools in secretion, induced by muscarinic agonists in porcine adrenal chromaffin cells, was studied. Activation of muscarinic receptors, as in other species, was found to increase inositol phosphate production including that of Ins(1,4,5)P3. Treatment of cells with thapsigargin, which is known to deplete Ins(1,4,5)P3-sensitive Ca2+ pools, eliminated the initial transient component of increases in the cytosolic free Ca2+ concentration ([Ca2+]in) induced by the muscarinic agonist, methacholine, in both the presence and the absence of extracellular Ca2+. Thapsigargin treatment also decreased methacholine-induced secretion by about 30% in the presence of extracellular Ca2+ and essentially eliminated secretion that occurred independently of extracellular Ca2+ (which was about 30% of the secretory response that occurred in the presence of extracellular Ca2+). Thapsigargin itself had no effect on inositol phosphate production. These results indicate that about 30% of muscarinic agonist-induced secretion is mediated by the release of Ca2+ from Ins(1,4,5)P3- and thapsigargin-sensitive intracellular Ca2+ pools. These results also suggest that Ca2+ influx activated by muscarinic agonists is not due to depletion of intracellular Ca2+ pools, as prior depletion of these pools had no effect on the portion of the methacholine-induced secretory response and [Ca2+]in signal that was dependent on extracellular Ca2+.

The effects of neuropeptides on mucous glycoprotein secretion from human nasal mucosa in vitro

The role of neuropeptides in the regulation of macromolecule secretion from human nasal mucosa is incompletely understood. Previous in vitro explant culture studies have demonstrated the effects of neuropeptides on lactoferrin release from serous cells and 3H-glucosamine labeled respiratory glycoconjugate secretion from mucus-containing cells. The generation of a new monoclonal antibody, 7F10, has led to the development of an ELISA for high molecular weight respiratory mucous glycoproteins (MGP). This ELISA was used to measure the ability of sensory, parasympathetic and sympathetic neuropeptides to stimulate MGP release from human nasal mucosal fragments in short term explant culture in vitro. Significant MGP release was stimulated by the sensory neuropeptides gastrin releasing peptide (10 μM GRP: 10.6% ± 2.4% increase, n = 8, P < 0.01 vs. control), substance P (1 μM SP: 12.5% ± 5.4%, n = 11, P < 0.05), neurokinin A (1 μM NKA: 17.8 ± 4.3%, n = 6, P < 0.01), while calcitonin gene related peptide (CGRP) was without effect. Vasoactive intestinal peptide (VIP), a neurotransmitter from parasympathetic nerves, induced significant dose dependent MGP secretion, but had no additive or inhibitory interaction with methacholine-induced secretion. Neuropeptide Y (NPY), present in sympathetic nerves, had no effect on MGP secretion. These observations correlate with the effects of neuropeptides on serous cell lactoferrin secretion, and the presence of specific GRP, SP, and VIP binding sites on human nasal submucosal glands that have been detected by autoradiography. GRP and tachykinins (SP and NKA) from sensory nerves, and VIP released during parasympathetic reflexes may signficantly stimulate mucous and serous cell secretion from human nasal mucosa in vivo.

Calcium Dependency of Muscarinic and Nicotinic Agonist‐Induced ATP and Catecholamine Secretion from Porcine Adrenal Chromaffin Cells

The secretion of catecholamines and ATP induced by cholinergic agonists and its dependence on extracellular Ca2+ were studied in cultured porcine adrenal chromaffin cells. Both nicotine and methacholine (a selective muscarinic agonist) induced secretion and increases in cytosolic free Ca2+ concentration ([Ca2+]in), although the activation of nicotinic receptors produced responses that were larger than those produced by activation of muscarinic receptors. The secretion and the increase in [Ca2+]in evoked by nicotine were completely dependent on extracellular Ca2+ and were blocked by prior depolarization of the cells with high extracellular K+ levels. In addition, nicotine induced significant 45Ca2+ influx. In contrast, the secretion and the increase in [Ca2+]in evoked by methacholine were partially dependent on extracellular Ca2+; methacholine also induced 45Ca2+ influx. Prior depolarization of the cells with high extracellular K+ levels did not block methacholine-induced secretion. In general, nicotinic responses were mediated by Ca2+ influx through voltage-dependent pathways. In contrast, muscarinic responses were dependent on both Ca2+ influx through an unknown mechanism that could not be inactivated by high K+ concentration-induced depolarization and presumably also intracellular Ca2+ mobilization.

Extracellular sodium is required for methacholine‐induced secretion of mucus glycoconjugates from canine tracheal explants

Extracellular sodium is known to influence secretion by certain secretory cells, possibly by mobilizing calcium from cellular stores or by altering intracellular pH via regulation of a Na(+)-H+ antiport system. Using canine tracheal explants, we determined whether agents which alter sodium fluxes are capable of modulating basal or cholinergically-induced secretion of mucus glycoconjugates. Methacholine, a cholinergic agonist, increased mucus secretion from explants incubated in the presence or absence of calcium, but had no effect on secretion when incubated in sodium-deficient media, indicating (a) that cholinergically-induced secretion can be mediated by mobilization of cellular calcium and (b) that extracellular sodium was required for this stimulatory effect. Several agents which increase intracellular sodium were tested for their effect on mucus secretion. Ouabain, a sodium pump inhibitor, and veratridine, a sodium channel activator, did not significantly affect control or methacholine-induced secretion; gramicidin, a sodium ionophore, also had no effect on basal release. Tetrodotoxin, a sodium channel inhibitor, was also without effect on basal or methacholine-stimulated mucus release. Agents which alter intracellular pH were also examined for their effects on basal or methacholine-induced glycoconjugate secretion. Amiloride, which decreases intracellular pH by inhibiting Na(+)-H+ exchange, produced a 19 per cent increase in basal secretion (not statistically significant), but had no effect on methacholine-induced secretion. An agent, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), which decreases intracellular pH by inhibiting HCO3(-)-Cl- exchange, elicited decreases in both basal and methacholine-induced secretion, but the inhibition did not reach statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Functionally distinct muscarinic receptors on gastric somatostatin cells

The present study was designed to examine the mode of action of muscarinic agonists on somatostatin secretion in intact gastric tissues, i.e., mucosal segments from the fundus and antrum of rat and the isolated luminally perfused mouse stomach. Methacholine caused similar decreases in somatostatin secretion in segments from the fundus (35 +/- 3%; P less than 0.001) and antrum (35 +/- 2%; P less than 0.001) of rat stomach, and in whole mouse stomach (43 +/- 3%; P less than 0.001). The decrease was the net effect of a dominant inhibition and a lesser stimulation of somatostatin secretion. Pretreatment with the permeant derivative of the acetomethoxy ester form of the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA/AM, 15 microM) caused a further decrease in methacholine-induced somatostatin secretion, implying that a stimulatory component existed that was mediated by intracellular calcium. Pretreatment with pertussis toxin (125 ng/ml) for 60 min converted the decrease in somatostatin secretion to an increase above basal levels. The increase induced by pretreatment with pertussis toxin was abolished by additional pretreatment with BAPTA/AM. Procaine (5 mM), which blocks release of calcium from intracellular stores, produced an effect on somatostatin secretion similar to that of BAPTA/AM. The results indicate that 1) methacholine exerts dual inhibitory and stimulatory effects on somatostatin cells of rat and mouse stomach, 2) the dominant effect is inhibitory and sensitive to pertussis toxin, and 3) a concurrent stimulatory effect, mediated by calcium, is unmasked after blockade of the inhibitory effect with pertussis toxin.

Prostaglandins alter methacholine-induced secretion in ferret in vitro trachea

The ferret trachea was mounted in an organ bath containing Krebs-Henseleit solution with additional bovine serum albumin (BSA). Tracheal secretions were collected and analyzed for albumin, and lysozyme, a specific marker of serous cell secretion. The total secretion volume and output and concentrations of albumin and lysozyme were calculated. Secretion was stimulated with methacholine (20 microM) (Mch), and the effects of the prostaglandins PGD2, PGE1, and PGF2 alpha on methacholine-induced secretion were studied. All responses were dose dependent. PGF2 alpha at 10(-5) M increased the volume of Mch-stimulated secretion twofold, the lysozyme output sixfold, and concentration over threefold, while decreasing the albumin transport by one-half. PGD2 at 10(-5) M reduced Mch-induced secretion volume to 75% control, increased albumin transport to 135%, without affecting lysozyme secretion. PGE1 at 10(-5) M increased Mch-stimulated albumin transport and concentration over twofold, decreased lysozyme release to less than one-third of control, and had no effect on secretion volume. PGE1 caused the albumin concentration to exceed that of the outer bath, indicating active transport. We conclude that prostaglandins selectively alter tracheal secretion induced by cholinergic stimuli.

A comparative study of gastric secretory stimulants in conscious dogs

1. In conscious dogs with gastric fistulae, Heidenhain pouches and Thomas duodenal fistulae, pentagastrin was found to be a more potent peak acid and pepsin stimulant in both innervated stomach and vagally denervated pouch than methacholine chloride. 2. Slopes of curves relating response to the logs of molar doses of pentagastrin and methacholine, at peak secretion, did not differ significantly. The maximal pentagastrin stimulated secretion from the pouch was smaller than that for methacholine; from the fistula they did not differ. 3. Ganglionic blockade depressed methacholine stimulated peak acid secretion, but did not affect pentagastrin stimulated acid secretion. Dose-response curves for methacholine-induced acid and pepsin secretion at the perigee did not differ from those obtained with ganglionic blockade. 4. Ganglionic blockade depressed pepsin secretion from the fistula whether stimulated with pentagastrin or methacholine. Pouch pepsin secretion was small and no difference between curves was seen.

Capsaicin and nicotine-sensitive afferent neurones and nasal secretion in healthy human volunteers and in patients with vasomotor rhinitis.

1. Applications of capsaicin, nicotine and methacholine were made locally onto the nasal mucosa in human controls and patients suffering from hyperreactive nasal disorders. Perception of sensation was registered as a sympton score and secretion quantified. The sensory reaction (irritation - pain) to capsaicin was similar in the three groups studied, i.e. controls, a group of patients with the diagnosis of vasomotor rhinitis and a group of patients with increased nasal secretion as the main symptom of the hyperreactive disorder. Nicotine induced only a mild itching sensation in the three groups. However, capsaicin and nicotine challenge caused a significantly larger secretory response in the last group than in the unselected vasomotor rhinitis group and in the control group. 2. Pretreatment with muscarinic receptor antagonists almost completely abolished the secretory response to both capsaicin and nicotine, and blocked methacholine-induced secretion. Furthermore, pretreatment with a combination of local anaesthetic and vasoconstrictor agent abolished the capsaicin-induced irritation, as well as the capsaicin- and nicotine-induced secretion on both the ipsilateral and the contralateral side. Therefore, no clearcut contribution seems to be exerted by locally released peptides from sensory neurones as direct trigger substances for the secretory response to capsaicin. 3. In conclusion, the nasal secretory response, in man, to both capsaicin and nicotine, seems to be mediated via cholinergic parasympathetic reflexes. In patients with hyperreactive non-allergic disorders of the nasal mucosa with rhinorrhea as the main complaint, the enhanced secretion may be due to a hyperreactive efferent cholinergic mechanism rather than hypersensitive irritant receptors on capsaicin- and nicotine-sensitive sensory neurones. Challenge with irritant agents seems a useful test for the evaluation of both afferent and efferent reflexogenic responses in hyperreactive disorders of the nasal mucosa.

Secretion of amylase from the rat parotid salivary gland after degeneration of the auriculotemporal nerve

The output of amylase into saliva secreted after injection of methacholine or substance P was increased after parasympathetic denervation, but the salivary concentration of amylase was unchanged. The increased output corresponded to the increased flow. Isoprenaline injected during the methacholineinduced secretion raised the output, more being secreted from the denervated than from the contralateral gland. Vasoactive intestinal peptide, given while substance P caused salivation, also increased the amylase output, but equally from the two glands.

Pathophysiology of rhinitis. 1. Assessment of the sources of protein in methacholine-induced nasal secretions.

Nasal provocation tests with normal saline and methacholine (MC) were performed in 25 atopic and 27 nonatopic subjects in an effort to assess the sources of protein in induced airway secretions. Nasal lavages obtained at baseline and after provocation were analyzed for albumin, total protein, secretory IgA (sIgA), and total IgA. Compared with baseline levels or saline provocation, MC provocation increased the secretion of albumin (p less than 0.025), total protein (p less than 0.001), sIgA (p less than 0.025), and total IgA (p less than 0.025), but did not significantly affect the relative proportions of albumin-to-total protein (albumin percent) or sIgA-to-total IgA (sIgA/total IgA ratio). Nasal pretreatment with atropine significantly inhibited MC-induced secretion of all 4 proteins, again without affecting the albumin percent or the sIgA/total IgA ratio. Because MC is known to stimulate atropine-inhibitable secretion of glandular products, these data suggest that sIgA and albumin may accompany glandular secretions. Immunohistochemical analyses of nasal turbinates confirmed that secretory component was found only on serous cells within submucous glands. Thus, it appears that cholinergic stimulation may regulate sIgA secretion and thereby participate in local nasal (and possibly respiratory tract) immunity.

Action of a novel drug (Zy 16039) on mucus secretion in the ferret isolated trachea in vitro.

1. The effect of 4-H-2-carboxamido-4-phenyl-thieno-[3,2c]-[1]-benzopyran (Zy 16039) was examined on the smooth muscle contraction, mucus secretion and albumin transudation in the ferret whole trachea in vitro. 2. Zy 16039 (0.1-20 microM) produced a concentration-dependent relaxation of the ferret trachea contracted by methacholine (1 microM) and phenylephrine (10 microM). The relaxations were about 20% of the full contractions. 3. Zy 16039 has no effect on the resting (zero) output of mucus in the ferret trachea. Methacholine-induced mucus secretion was significantly inhibited by Zy 16039, whereas phenylephrine-induced secretion was significantly increased. 4. Methacholine-induced secretion of lysozyme, a marker of serous cell secretion, was inhibited by Zy 16039 both with regard to output and concentration of lysozyme. In contrast, Zy 16039 significantly increased the output of lysozyme due to phenylephrine, with no effect on concentration. 5. Zy 16039 had no significant effect on the rate of output of fluorescent albumin through the tracheal wall. However the concentration of albumin in the mucus samples was changed because of the effect of Zy 16039 on mucus secretion induced by methacholine and phenylephrine. 6. We conclude that Zy 16039 relaxes airway smooth muscle, and either promotes or inhibits mucus secretion depending on its source. It has qualitatively similar actions to vasoactive intestinal peptide.

Serotonin in nasal secretion.

The aim of this study was to investigate the serotonin content in nasal secretion. Histamine- and methacholine-induced nasal secretions were collected during a 5-min period after challenge in 33 normal subjects. Serotonin was determined radioenzymatically and was found in 66% of pure, blown secretions. The median concentration of serotonin in histamine- and methacholine-induced secretions was 6.3 nmol/l (range less than 1.6-52.0) and 2.3 nmol/l (range 1.6-140.0) (NS), respectively. The serotonin concentration in allergen-induced nasal secretions in 7 rhinitis patients was 0.8 to 159 nmol/l, median 10.4 nmol/l which did not differ from the serotonin levels in the normal subjects. The serotonin concentration in nasal lavage fluids in 5 subjects was low (below the detection limit in 78% of the samples). Further studies of serotonin in patients with nasal hypersecretion are indicated.

The effect of vasoactive intestinal peptide on smooth muscle tone and mucus secretion from the ferret trachea.

The effect of vasoactive intestinal peptide (VIP) was examined on the smooth muscle contraction and mucus secretion produced by methacholine and phenylephrine in the ferret whole trachea in vitro. VIP (0.5 to 800 nM) produced a concentration-dependent relaxation of the ferret trachea contracted by methacholine (1 microM) and phenylephrine (10 microM). The concentration-response curves for methacholine- and phenylephrine-induced contractions were both shifted to the right by VIP (0.1 microM). Methacholine-induced secretion was inhibited in a concentration-dependent manner by VIP, whereas that due to phenylephrine was enhanced. The concentration-response curve for methacholine-induced secretion was shifted to the right by VIP, whereas the curve for phenylephrine was shifted to the left. Methacholine produced a concentration-dependent increase in the rate of output of lysozyme from the ferret trachea with no corresponding increase in the concentration of lysozyme in the mucus. Phenylephrine produced a concentration-dependent increase in the rate of output and in the concentration of lysozyme. VIP (0.1 microM) significantly increased the concentration of lysozyme in the mucus produced by methacholine with no increase in the rate of lysozyme output. However, the rate of lysozyme output due to phenylephrine was significantly increased by VIP (0.1 microM) with no increase in concentration. We suggest that VIP inhibits secretion from mucous cells stimulated by methacholine, and enhances the secretion produced by phenylephrine from serous cells.

Biochemical analysis of nasal secretions induced by methacholine, histamine, and allergen provocations.

Nasal provocation tests with methacholine, histamine, and allergen were performed outside the pollen season in 26 pollen-allergic subjects with the aim of sampling nasal secretions for biochemical characterization. Sugar analyses showed that methacholine-induced secretions were a mixture of serous and mucous glycoproteins. Compared with published sputum values, the levels of proteins and sugars were approximately 5 times lower in the methacholine-induced secretions (protein, 6 mg/ml; hexose, 2 mg/ml), whereas the albumin concentrations were comparable (1 mg/ml). Histamine-induced secretions as well contained a mixture of serous and mucous glycoproteins and a high albumin level (3 mg/ml), indicating a relatively higher degree of transudation than in methacholine- and allergen-induced secretions. Allergen-induced secretions had a low dry weight (mean, 19 mg/g; p less than 0.05) and protein (mean, 4 mg/ml; p less than 0.01) content compared with that in methacholine- and histamine-induced secretions; they contained mainly mucous glycoprotein, and the albumin level was relatively low. Thus, nasal secretions have lower dry weight, sugar and protein content than does sputum; histamine provokes marked transudation; methacholine and allergen do not; methacholine and histamine produce a mixture of serous and mucous glycoproteins; allergen produces mainly mucous glycoproteins.