Human Bronchial Preparations Research Articles

Characterization of V0162, a new long-acting antagonist at human M3 muscarinic acetylcholine receptors

The anticholinergic properties of the mequitazine enantiomer V0162 make it a drug candidate for the treatment of chronic obstructive airway diseases. Here, we compared V0162’s in vitro pharmacological activity at recombinant human M3 muscarinic acetylcholine receptors (hM3Rs) with that of other anticholinergics, using (i) a radioligand binding assay, (ii) a functional reporter gene assay and (iii) a bronchoconstriction inhibition assay on human bronchial preparations. V0162 had high affinity for hM3Rs, with a pKi varying from 9.01 after a 2h incubation to 9.21 after 23h. The other mequitazine enantiomer (V0114) was less potent. V0162 displayed rapid off-kinetics and a biphasic time course of binding. V0162 was found to be an antagonist behaving as an inverse agonist for hM3R-mediated reporter gene activation, with much the same efficacy as atropine, ipratropium and tiotropium. However, in contrast to ipratropium and atropine, V0162’s inhibitory potency was only slightly affected by compound washout. V0162 antagonized acetylcholine-mediated contractions in a human bronchial preparation; the pA2 values increased with the incubation time (up to 2h). Moreover, there was a progressive increase in V0162’s ability to inhibit electrically-induced contractions, which persisted after compound washout. In conclusion, V0162 is the most active mequitazine enantiomer at hM3Rs and shows a complex pattern of binding to the membrane compartment. These particular features may be of therapeutic value when persistent antagonism at hM3Rs is required.

Bronchodilatory and Anti-Inflammatory Effects of ASM-024, a Nicotinic Receptor Ligand, Developed for the Treatment of Asthma

Conventional asthma and COPD treatments include the use of bronchodilators, mainly β2-adrenergic agonists, muscarinic receptor antagonists and corticosteroids or leukotriene antagonists as anti-inflammatory agents. These active drugs are administered either separately or given as a fixed-dose combination medication into a single inhaler. ASM-024, a homopiperazinium compound, derived from the structural modification of diphenylmethylpiperazinium (DMPP), has been developed to offer an alternative mechanism of action that could provide symptomatic control through combined anti-inflammatory and bronchodilator properties in a single entity. A dose-dependent inhibition of cellular inflammation in bronchoalveolar lavage fluid was observed in ovalbumin-sensitized mice, subsequently treated for 3 days by nose-only exposure with aerosolized ASM-024 at doses up to 3.8 mg/kg (ED50 = 0.03 mg/kg). The methacholine ED250 values indicated that airway hyperresponsivenness (AHR) to methacholine decreased following ASM-024 administration by inhalation at a dose of 1.5 mg/kg, with a value of 0.145±0.032 mg/kg for ASM 024-treated group as compared to 0.088±0.023 mg/kg for untreated mice. In in vitro isometric studies, ASM-024 elicited dose-dependent relaxation of isolated mouse tracheal, human, and dog bronchial preparations contracted with methacholine and guinea pig tracheas contracted with histamine. ASM-024 showed also a dose and time dependant protective effect on methacholine-induced contraction. Overall, with its combined anti-inflammatory, bronchodilating and bronchoprotective properties, ASM-024 may represent a new class of drugs with a novel pharmacological approach that could prove useful for the chronic maintenance treatment of asthma and, possibly, COPD.

PGE2 receptor (EP4) agonists: Potent dilators of human bronchi and future asthma therapy?

BackgroundAsthma and chronic obstructive pulmonary disease are characterized by inappropriate constriction of the airway smooth muscle. In this context, the physiological response of the human airways to selective relaxant agonists like PGE2 is highly relevant. The aim of this study was thus to characterize the PGE2 receptor subtypes (EP2 or EP4) involved in the relaxation of human bronchial preparations. MethodsHuman bronchial preparations cut as rings were mounted in organ baths for isometric recording of tension and a pharmacological study was performed using selective EP2 or EP4 ligands. ResultsIn the presence of a thromboxane TP receptor antagonist and indomethacin, PGE2 induced the relaxation of human bronchi (Emax = 86 ± 04% of papaverine response; pEC50 value = 7.06 ± 0.13; n = 6). This bronchodilation was significantly blocked by a selective EP4 receptor antagonist (GW627368X, 1 and 10 μmol/L) with a pKB value of 6.38 ± 0.19 (n = 5). In addition, the selective EP4 receptor agonists (ONO-AE1-329; L-902688), but not the selective EP2 receptor agonist (ONO-AE1-259), induced potent relaxation of bronchial preparations pre-contracted with histamine or anti-IgE. ConclusionPGE2 and EP4 agonists induced potent relaxations of human bronchial preparations via EP4 receptor. These observations suggest that EP4 receptor agonists could constitute therapeutic agents to treat the increased airway resistance in asthma.

Effect of cold storage on cholinergic responses induced by electrical field stimulation in human bronchi

The aim of the present study was to examine the effects of cold storage on the responses induced by electrical field stimulation (EFS) in human bronchial preparations. Responses induced by EFS and acetylcholine were studied in human bronchial rings mounted in organ baths, either on the day of surgery or after storage at 4 °C in Krebs–Henseleit solution for 24 and 48 h, respectively. The responses induced by EFS were studied at different voltages (20, 40 and 60 V) and at a range of frequencies (2, 4, 8, 10, 30 and 60 Hz). EFS induced a triphasic response, consisting of a cholinergic contraction, followed by a relaxation and subsequently a slow sustained contraction. The amplitude of the EFS-induced response was enhanced with increasing voltages and increasing frequencies. None of the three EFS-induced phases were significantly altered by cold storage at 24 h, whereas storage for 48 h significantly decreased the reactivity of the preparations. Likewise, the contractions induced by acetylcholine were unaltered after 24 h, but significantly depressed after 48 h. These results suggest that the reactivity of human bronchial preparations to EFS is not altered when tissues are conserved for 24 h, whereas prolonged storage should be avoided.

Cholinesterase activity in human pulmonary arteries and veins: correlation with mRNA levels

Isolated intact human pulmonary arteries and veins were used to determine the acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) activities in the absence or presence of two selective cholinesterase (ChE) inhibitors, iso-OMPA or BW284c51, respectively. These results were compared with the mRNA levels for each enzyme in human pulmonary vessels. Total ChE activities measured in presence of acetylthiocholine (ACTI, 1 mM) in intact vascular preparations were 45 ± 04 and 114 ± 07 mU/g tissue in human pulmonary arteries (n = 14) and veins (n = 14), respectively. These activities were completely abolished in presence of 10 μM neostigmine. In both types of vessels AChE and BChE activities were observed. These activities were at least 2-fold higher in human pulmonary veins when compared with arteries and were correlated with the accumulation of the corresponding transcripts (n = 8). In each type of vessel, similar total ChE activities were detected in homogenized and intact preparations, while in human bronchial preparations this activity was 5-fold higher in homogenates than in intact preparations. Together these results provide evidence that the ChE activities in human pulmonary vessels may be extracellular and that the higher activity measured in veins as compared to arteries was associated with the differential accumulation of the corresponding transcripts.

L-CARNITINE DOES NOT EXERT ANY IN VITRO RELAXANT EFFECT IN GUINEA PIG TRACHEA, LUNG PARENCHYMA AND HUMAN BRONCHIAL TISSUE

The aim of the present study was to investigate the probable in vitro relaxant effect of carnitine in guinea pig trachea, guinea pig lung parenchymal strips, and human bronchial tissue. It was suggested by an in vivo study that carnitine pretreatment prevented the subclinic bronchospasm in children who underwent chronic hemodialysis. Tracheal and lung parenchymal preparations of 10 guinea pigs and 5 human bronchial tissues were prepared and mounted in 20-mL organ baths. In the first series of experiments, contractions to carbachol and histamine (10 -9 to 10 -3 M) were compared after the tissues were incubated with different concentrations of L-carnitine (10 -6 to 10 -4 M). pD 2 values were compared with analysis of variance (ANOVA) and P <. 05 was considered as significant. In the second part of experiments, the inhibitory effect of L-carnitine (10 -9 to 10 -3 M) was investigated on the sustained contractions of preparations to carbachol (10 -6 M) and histamine (10 -5 M). In the first part of the study pD 2 values obtained with carbachol were 6.48 ± 0.09, 5.42 ± 0.05, and 6.48 ± 0.02 for guinea pig trachea, guinea pig lung parenchymal strips, and human bronchial tissues, respectively. pD 2 values obtained with histamine were 5.34 ± 0.10, 5.74 ± 0.06, and 6.32 ± 0.03 for guinea pig trachea, guinea pig lung parenchymal strips, and human bronchial tissues, respectively. No significant difference was observed between the pD 2 values before and after incubation with carnitine (P >. 05). In the second part of the study, only 10 -4 M L-carnitine exerted an insignificant relaxant effect (6.16% ± 1.22% on carbachol induced contractions and 4.48% ± 0.85% on histamine induced contractions) in guinea pig trachea. Our results show that L-carnitine exerts no in vitro relaxant effect in guinea pig trachea, guinea pig lung parenchymal strips, and human bronchial preparations.

EGTA treatment of human airways in vitro unmasks M1/MUC5AC mucin in submucosal glands.

Mucin staining can be used to evaluate secretory activity of human airways. However, mucin epitopes may be masked by physicochemical properties of the secretions. The aim of this investigation was to examine the effects of the calcium chelator, ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) on the detection of M1/MUC5AC mucin in isolated human bronchial preparations. Immunohistochemical investigation and immunoradiometric assays with anti-M1 monoclonal antibodies (Mabs) were used to detect M1/MUC5AC mucin derived from bronchial preparations with an intact surface epithelium, or in tissues where the epithelium had been removed (rubbed preparations). The Mabs labelled both epithelial goblet cells and submucosal glandular cells in EGTA (4 mM)-exposed bronchial preparations, while only goblet cells were stained in EGTA (0.4 mM)-exposed tissues. The quantities of M1/MUC5AC mucin detected in either the bronchial fluids derived from EGTA (4 mM)-exposed intact and rubbed preparations or in bronchial fluids treated with EGTA (4 mM) were significantly increased by two-fold when compared with untreated control values (p<0.001). In addition, lactate dehydrogenase (LDH) activity and protein measurements were unaltered during exposure of human airways to EGTA (4 mM) suggesting that this treatment did not affect tissue viability. These results provide evidence that ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (4 mM) facilitates the detection of M1/MUC5AC mucin by altering the physicochemical properties of respiratory mucin, thereby exposing epitopes with which anti-M1 monoclonal antibodies are reactive. This will allow more accurate measurement of secretory activity in human airways in vitro.

ATP induced MUC5AC release from human airways in vitro.

Chronic airway diseases are often associated with marked mucus production, however, little is known about the regulation of secretory activity by locally released endogenous mediators. This investigation was performed to determine the release of MUC5AC mucin from human bronchial preparations using the purinergic agonists adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP). Immunohistochemical and immunoradiometric assays (IRMA) were used to detect the MUC5AC mucin. Immunohistochemical analysis were performed using individual 1-13 M1 and 21 M1 MAbs recognizing a recombinant M1 mucin partially encoded by the MUC5AC gene. IRMA measurments were performed using a mixture of eight anti-M1 mucin MAbs (PM8), which included both 1-13 M1 and 21 M1 MAbs. Lysozyme and protein were also measured in the biological fluids derived from human bronchial preparations obtained from patients who had undergone surgery for lung carcinoma. The anti-M1 monoclonal antibodies labelled epithelial goblet cells. After challenge of human bronchial preparations with ATP, the goblet cells exhibited less staining. In contrast, UTP did not alter the immunolabelling of goblet cells. MUC5AC mucin in the bronchial fluids derived from ATP-challenged preparations was increased while UTP had no effect on release. ATP did not alter either the quantities of lysozyme or protein detected in the biological fluids. These results suggest that ATP may regulate epithelial goblet cell secretion of MUC5AC mucin from human airways in vitro.

MUC5AC mucin release from human airways in vitro: effects of indomethacin and Bay X1005.

Increased secretion of mucus is a hallmark of many respiratory diseases and contributes significantly to the airflow limitation experienced by many patients. While the current pharmacological approach to reducing mucus and sputum production in patients is limited, clinical studies have suggested that drugs which inhibit the cyclooxygenase and/or 5-lipoxygenase enzymatic pathways may reduce secretory activity in patients with airway disease. This study was performed to investigate the effects of indomethacin (cyclooxygenase inhibitor) and Bay x 1005 (5-lipoxygenase inhibitor) on MUC5AC release from human airways in vitro. An immunoradiometric assay was used to determine the quantities of MUC5AC present in the biological fluids derived from human airways in vitro. The measurements were made with a mixture of eight monoclonal antibodies (MAbs; PM8) of which the 21 M1 MAb recognized a recombinant M1 mucin partially encoded by the MUC5AC gene. The quantities of MUC5AC detected in the biological fluids derived from human bronchial preparations were not modified after treatment with indomethacin (cyclooxygenase inhibitor) and/or an inhibitor of the 5-lipoxygenase metabolic pathway (BAY x 1005). These results suggest that the cyclooxygenase and 5-lipoxygenase metabolic pathways play little or no role in the release of MUC5AC from human airways.

Phospholipase A&lt;SUB&gt;2&lt;/SUB&gt; augments contraction and intracellular calcium mobilization through thromboxane A&lt;SUB&gt;2&lt;/SUB&gt; in bovine tracheal smooth muscle

A series of monoclonal antibodies which bind to a mucin known as M1 (anti-M1 MAbs) have also been shown to detect the product of the human gene MUC5AC. The aim of this investigation was to determine the concentration of the M1 mucin in the surface epithelium of human bronchial preparations by means of immunohistochemistry and in the bronchial fluid derived from human airways by means of an immunoradiometric assay. Human bronchial ring preparations from the resection material of 20 patients were challenged with methacholine, leukotriene D4, or anti-immunoglobulin E. Experiments were performed in preparations with an intact epithelium as well as in tissues in which the epithelium had been mechanically removed. The anti-M1 MAbs stained the goblet cells in the epithelium intensely and there was also light and less uniform staining in the submucosa. The M1/MUC5AC mucin in the fluids secreted by the bronchial preparations was not modified during either the experimental protocol or stimulation with the different secretagogues. However, in preparations in which the epithelium had been removed, there was a significant reduction in the amount of M1/MUC5AC mucin detected. These data suggest that the M1/MUC5AC mucin detected in the biological fluids produced by human airways in vitro may be released constantly, and principally from the goblet cells in the epithelial layer.

M1/MUC5AC mucin released by human airways in vitro.

A series of monoclonal antibodies which bind to a mucin known as M1 (anti-M1 MAbs) have also been shown to detect the product of the human gene MUC5AC. The aim of this investigation was to determine the concentration of the M1 mucin in the surface epithelium of human bronchial preparations by means of immunohistochemistry and in the bronchial fluid derived from human airways by means of an immunoradiometric assay. Human bronchial ring preparations from the resection material of 20 patients were challenged with methacholine, leukotriene D4, or anti-immunoglobulin E. Experiments were performed in preparations with an intact epithelium as well as in tissues in which the epithelium had been mechanically removed. The anti-M1 MAbs stained the goblet cells in the epithelium intensely and there was also light and less uniform staining in the submucosa. The M1/MUC5AC mucin in the fluids secreted by the bronchial preparations was not modified during either the experimental protocol or stimulation with the different secretagogues. However, in preparations in which the epithelium had been removed, there was a significant reduction in the amount of M1/MUC5AC mucin detected. These data suggest that the M1/MUC5AC mucin detected in the biological fluids produced by human airways in vitro may be released constantly, and principally from the goblet cells in the epithelial layer.

Prostanoid receptors involved in the relaxation of human bronchial preparations.

1. Iloprost and cicaprost (IP-receptor agonists) induced relaxations in the histamine- (50 microM) contracted human bronchial preparations (pD2 values, 6.63+/-0.12 and 6.86+/-0.08; Emax values, 90+/-04 and 65+/-08% of the papaverine response for iloprost (n=6) and cicaprost (n=3), respectively). 2. Prostaglandin E2 (PGE2) and misoprostol (EP-receptor agonist) relaxed the histamine-contracted human bronchial preparations (pD2 values, 7.13+/-0.07 and 6.33+/-0.28; Emax values, 67+/-04 and 57+/-08% of the papaverine response for PGE2 (n=14) and misoprostol (n=4), respectively). In addition, both relaxations were inhibited by AH6809 (DP/EP1/EP2-receptor antagonist; 3 microM; n=5-6). 3. The PGE2-induced relaxations of human bronchial preparations were not modified by treatment with AH23848B (TP/EP4-receptor antagonist; 30 microM; n=4). 4. The contracted human bronchial preparations were significantly relaxed by prostaglandin D2 (PGD2) or by BW245C a DP-receptor agonist. However, these responses did not exceed 40% of the relaxation induced by papaverine. In addition, the relaxations induced by PGD2 were significantly inhibited by treatment with a DP-receptor antagonist BWA868C (0.1 microM; n=3). 5. These data suggest that the relaxation of human isolated bronchial preparations induced by prostanoids involved IP-, EP2- and to a lesser extent DP-receptors but not EP4-receptor.

The relevance of resting tension to responsiveness and inherent tone of human bronchial smooth muscle.

1. In the present study the effects of resting tension on isometric responses of human airway smooth muscle to contractile and relaxant stimuli were investigated. Also, its effects on inherent smooth muscle tone were examined, in an effort to determine a pre-defined resting tension which can be considered optimal for in vitro studies. 2. Bronchial ring preparations (2-4 mm internal diameter) were suspended in tissue baths at a range of levels of resting tension (200-1600 mg). The responses to electrical field stimulation (EFS, 30 V, 0.2 ms, 8-30 Hz), carbachol (3 microM), isoprenaline (1 microM) and the 5-lipoxygenase inhibitor, zileuton (10 microM) were investigated along with the ability of the preparations to recover stable resting tension after 60 min of washing post challenge. 3. EFS induced monophasic contractions at low stimulation frequency (8 Hz). However, with increasing frequency and tension (15 and 30 Hz; > 400 mg) contractile responses were accompanied by a relaxant component. The magnitude of contractile responses increased with increasing resting tension to a plateau at between 500 and 700 mg. Relaxant responses when present, increased in magnitude with increasing resting tension. 4. The level of resting tension did not significantly alter responses to carbachol, but tissues at tensions > or = 1000 mg showed poor tension recovery after washing. Isoprenaline-induced relaxations increased with increasing resting tension (P<0.05) and tension recovery after washing was complete. The 5-lipoxygenase sensitive portion of the tension (33+/-4%) was not altered by the level of resting tension. 5 These results suggest that in human bronchial ring preparations of 2-4 mm internal diameter, resting tensions within the range 400-1000 mg could be considered optimal for isometric tension recordings of protocols involving both contraction and relaxation procedures.

Muscarinic inhibitory autoreceptors in different generations of human airways.

The present study was undertaken to investigate the functional presence of inhibitory muscarinic M2 autoreceptors on postganglionic cholinergic nerve endings in different generations of human airways. To this end, the effects of the M2-selective muscarinic receptor antagonists AQ-RA 741 and gallamine were studied on electrical field stimulation-induced twitch contractions of preparations from trachea and from bronchial airways of varying diameter. Furthermore, electrically evoked release of endogenous acetylcholine from human bronchial preparations, and the effect of the muscarinic receptor antagonist atropine thereon, was measured by high-performance liquid chromatography. On average, twitch contractions were significantly but only slightly (11 to 15%) potentiated by M2-selective concentrations of AQ-RA 741 and gallamine, despite approximately half of the preparations showing no potentiation at all. A subdivision into airway generations showed that M2 autoreceptor function was not readily detectable in bronchioles and subsegmental bronchi. By contrast, both with AQ-RA 741 and gallamine a clear potentiation (26 to 36%) of the twitch contractions was observed in approximately half of the terminal bronchi and in all central airway preparations. Moreover, the evoked release of endogenous acetylcholine in terminal and subsegmental bronchi was significantly facilitated by atropine, to 162 to 189% of controls. These results provide strong and partly direct evidence for the existence of inhibitory muscarinic M2 receptors on postganglionic cholinergic nerve endings in human central airways and subsegmental and terminal bronchi, but not in bronchioli. It remains to be established, however, why these M2 receptors exhibit a rather variable functionality in regulating cholinergic nerve-mediated contraction in different airway generations.

Antagonism of β-adrenoceptor-mediated relaxations of human bronchial smooth muscle by carbachol

Activation of muscarinic M 2 receptors has been suggested to account, in part, for the reduced relaxant potency of β-adrenoceptor agonists in canine and guinea-pig tracheal smooth muscle pre-contracted with muscarinic agonists as compared to histamine. The aim of the present study was to determine whether the potency of isoprenaline is reduced in human bronchial ring preparations pre-contracted with carbachol as compared to histamine and whether activation of muscarinic M 2 receptors contributes to this effect. Cumulative concentration-effect curves to isoprenaline were obtained in the absence and presence of muscarinic M 2 receptor antagonism by methoctramine (0.3 μM) in bronchial ring preparations pre-contracted to equivalent isometric tensions with either histamine (10 μM) or carbachol (1 μM). The relaxant potency of isoprenaline was reduced in preparations pre-contracted with carbachol compared to histamine, but there was no significant effect of muscarinic M 2 receptor antagonism on either the potency or maximal relaxation by isoprenaline. In conclusion, increased functional antagonism of β-adrenoceptor-mediated relaxation by muscarinic agonists can be demonstrated in human bronchial smooth muscle, but muscarinic M 2 receptors do not appear to contribute to this effect.

New data concerning the antianaphylactic and antihistaminic activity of nimesulide.

The time to respiratory crisis in ovalbumin-sensitised guinea-pigs following exposure to aerosol administered antigen was dose dependently delayed by inhalation of nimesulide (0.1% to 1%), whereas indomethacin had no effect. At the same time, nimesulide significantly reduced blood histamine concentrations, in contrast to the slight increase observed with indomethacin. In human bronchial muscle preparations, nimesulide, but not indomethacin, antagonised H1-histamine-receptor activation by histamine and was without effect on acetylcholine-induced responses. Bronchoconstriction was also elicited in anaesthetised guinea-pigs by intravenous acetaldehyde (5% in saline, 1 ml/kg). This effect, which is paralleled by a rise in blood histamine concentrations, was significantly attenuated by inhaled nimesulide (0.1% to 1%), but not by indomethacin (1%). These data, which further support the antihistaminic and antiallergic activity of nimesulide, may have therapeutic relevance in patients who are affected by inflammation of the respiratory tract and who also have a history of allergic bronchoconstriction.

Human bronchial cyclic nucleotide phosphodiesterase isoenzymes: biochemical and pharmacological analysis using selective inhibitors.

1 The aims of the present study were to characterize the cyclic nucleotide phosphodiesterase (PDE) isoenzyme activities present in human bronchi and to examine the ability of selective isoenzyme inhibitors to relax histamine and methacholine precontracted preparations of human bronchi. 2 Three separations of pooled human bronchial tissue samples were performed. Ion-exchange chromatography showed that the soluble fraction of human bronchial preparations contains PDE I, II, III, IV and V isoenzyme activities. Multiple forms of PDE I and PDE IV were observed and PDE IV was the main cyclic AMP hydrolytic activity. 3 3-Isobutyl-l-methylxanthine (IBMX) non-selectively inhibited all separated isoenzyme activities. Zaprinast selectively inhibited PDE V, but also effectively inhibited one of the two PDE I isoforms identified. The PDE IV selective inhibitors rolipram and RO-201724, inhibited the PDE IV activities as did the dual PDE III/IV inhibitor, Org 30029. Org 9935, a PDE III selective inhibitor, potently attenuated part of the PDE IV activity peak in one of three separations performed, indicating that some PDE III activity may co-elute with PDE IV under the experimental conditions employed. 4 PDE IV-selective (rolipram), PDE III-selective (Org 9935) and dual PDE III/IV (Org 30029) inhibitors were effective relaxants of human bronchial smooth muscle. The PDE V/PDE I inhibitor, zaprinast was relatively ineffective. 5 The present study demonstrates in human bronchi, as in animal airways smooth muscle, that inhibitors of PDE III, PDEIV and dual PDE III/IV have potentially useful bronchodilator activity and are worthy of further consideration as anti-asthma drugs.

EFFECTS OF KETAMINE ON ISOLATED HUMAN BRONCHIAL PREPARATIONS

The bronchodilator effects of ketamine were examined in human bronchial preparations contracted maximally with histamine, acetylcholine, barium chloride or potassium chloride. Antagonism between ketamine and either histamine or acetylcholine was examined also. Ketamine caused bronchial relaxation irrespective of the constricting agent, and exerted a partial and non-competitive antagonism to histamine and acetylcholine. Propranolol and indomethacin did not inhibit the effect of ketamine, excluding the involvement of beta activation and of prostaglandins.

Human isolated bronchial muscle preparations from asthmatic patients: Effects of indomethacin and contractile agonists

Airway reactivity to histamine was determined in a group of non-asthmatic and asthmatic patients prior to thoracotomy. The latter group was more reactive to histamine provocation than the former (PC 40: 28.40 ± 6.27 mg/ml and 1.15 ± 0.19 mg/ml, respectively). Subsequent to the surgical intervention, isolated human bronchial muscle preparations were obtained from both groups (15 non-asthmatic and 5 asthmatic subjects). Histamine concentration-effect curves were generated both in the absence and in the presence of indomethacin (1.7 μM; 30 min). Neither the basal tone nor the histamine response and sensitivity of the preparations were altered by the antiinflammatory drug. In bronchial preparations from one asthmatic subject, indomethacin significantly reduced the prostaglandin production during histamine contraction. Prostaglandin E 2 and F 2α contracted isolated human bronchial muscle preparations from these asthmatic individuals. These data suggest that endogenous prostaglandins may not regulate the contractile response to histamine in vitro.

Vasorelaxant effects of atrial peptide II on isolated human pulmonary muscle preparations

Isolated human pulmonary arterial preparations were approximately 10-fold more sensitive to atrial peptide II than venous preparations (pD 2 values: 7.11 ± 0.14 and 6.17 ± 0.14, respectively). Atrial peptide II did not relax isolated human bronchial muscle preparations (pD 2 value: > 5.5). These data demonstrate that atrial peptide II is a selective relaxant agent in isolated human pulmonary vascular muscle preparations with no effect on isolated human airway muscle preparations.