The non-adrenergic, non-cholinergic response counteracts changes in guinea-pig airway tone with and without sympathetic activation.

1. We examined whether the non-adrenergic, non-cholinergic (NANC) neural response can counteract changes in smooth-muscle tone with and without simultaneous sympathetic activation in guinea-pig airways. 2. Isolated airway preparations were pretreated with indomethacin (10 microM) and incubated with either atropine (1 microM) and guanethidine (10 microM) or atropine (1 microM) alone. The response to electrical field stimulation (EFS: 1200 mA, 0.5 ms, 3 Hz for 240 s) was studied at various levels of tone prior to EFS: first without induced tone, then at a moderate tone induced by histamine (0.3 microM) and finally at a high tone induced by histamine (6 microM). 3. The response to EFS was a contraction when the tone prior to EFS was low and a relaxation when the tone prior to EFS was high. These responses converged towards a similar level of tone, in the distal trachea and in the main bronchus, with and without guanethidine. 4. The mean (s.e. mean) level of tone towards which the responses to EFS converged was lower after incubation with atropine alone compared with incubation with atropine and guanethidine, both in the distal trachea [8 (1)% compared with 30 (6)% of maximum tone] and in the main bronchus [28 (4)% compared with 57 (2)% of maximum tone]. In separate experiments, the guanethidine-induced effect on the responses to EFS was imitated by propranolol (1 microM) but not by prazosin (0.3 microM) and yohimbine (1 microM). 5. These findings indicate that the NANC neural response can counteract changes in airway smooth-muscle tone via a contraction or via a relaxation, depending on the tone prior to activation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bronchial hyperresponsiveness, epithelial damage, and airway eosinophilia after single and repeated allergen exposure in a rat model of anhydride-induced asthma

Bronchial hyperresponsiveness (BHR) and damage of the epithelium, as well as eosinophilia in the airway wall, induced by trimellitic anhydride (TMA) in sensitized brown Norway rats were studied. Rats were challenged once or seven times with aerosol of TMA conjugated to rat serum albumin (TMA-RSA) 3 weeks after intradermal TMA sensitization. Airway responsiveness (-log PC₃₀₀ of acetylcholine i.v.) was measured 24 h after allergen challenge. Epithelial lesion and eosinophil infiltration in the airway walls were quantified under light microscopy, and TMA-specific IgE and IgG in serum were evaluated with ELISA. High levels of TMA-specific IgE and IgG were found in all rats in the sensitized groups compared to nonsensitized groups ( P < 0.001). Repeated allergen challenges of 0.03% TMA-RSA for 7 consecutive days enhanced the level of TMA-specific IgG, compared to single challenge ( P < 0.05). Single allergen challenge of 0.3% TMA-RSA had a nonsignificant tendency to produce BHR in sensitized rats compared to nonsensitized rats ( P =0.06). However, repeated allergen challenges (0.003% and 0.03% TMA-RSA for 7 consecutive days) produced significant BHR in sensitized rats ( P < 0.05). Furthermore, repeated low-dose (0.003%) TMA-RSA challenge produced more BHR than a 10 times higher single dose (0.03%) ( P < 0.05). Slight damage of the airway epithelium was seen in sensitized and repeat-challenged groups. However, bronchial eosinophilia was found in the sensitized and single-challenged groups, but not in nonsensitized nonchallenged, and sensitized repeat-challenged groups ( P < 0.005). We conclude that the brown Norway rat can be sensitized with TMA, and that repeated low-dose allergen challenges produce slight epithelial damage and BHR which is independent of ongoing eosinophilia in the airway wall.     

Bradykinin-induced release of thromboxane B2 into bronchoalveolar lavage fluid of guinea pigs: relationship to airflow obstruction

The aim of this study was to evaluate the role of thromboxane A₂ in bradykinin-induced airflow obstruction in guinea pig in vivo. Airway insufflation pressure (P_i) was measured to assess airflow obstruction and the thromboxane B₂ (a stable metabolite of thromboxane A₂) concentration in bronchoalvelolar lavage fluid was determined by radioimmunoassay. The animals were pretreated with propranolol (1 mg/kg i.v.) and suxamethonium (5 mg i.v.) prior to bradykinin administration. Bradykinin instillation into the trachea (300 nmol) induced a P_i increase (47.5 ± 8.3 cm H₂O versus 23.8 ± 1.5 in sham) and significant thromboxane B₂ release into bronchoalveolar lavage fluid (79 ± 19 pg/ml versus 19 ± 6 in sham). A thromboxane synthase inhibitor (OKY-046, 30 mg/kg i.v.; ((E-E)-3-[p(1H-imidazole-1-yl-methyl) phenyl]-2-propenoic acid hydrochloride mono-hydrate)) or a thromboxane A₂ receptor antagonist (ICI192,605, 0.5 mg/kg i.v.; (4-(Z)-6-(2-o-chloro-phenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl)hexenoic acid)) reduced the P_i increase evoked by bradykinin (38.7 ± 3.8 and 40.6 ± 3.8 cm H₂O, respectively). OKY-046 abolished the thromboxane B₂ release. A platelet-activating factor receptor antagonist, WEB2086 (1 mg/kg i.v.; (3-[4-(chlorophenyl)-9-methyl-6H-thienol [3,2-f][1,2,4]trizolo-[4,3-a][1,4] diazepin-2-yl]1-4-(4-morpholinyl)-1-propanon) did not significantly affect any measured parameter. We conclude that, in guinea pigs, bradykinin-induced airway effects are associated with a local thromboxane A₂ release.     

Salmeterol, formoterol, and salbutamol in the isolated guinea pig trachea: differences in maximum relaxant effect and potency but not in functional antagonism.

BACKGROUND--Formoterol and salmeterol are new long acting beta 2 adrenoceptor agonists. The maximum relaxant effect, potency and functional antagonism against carbachol induced contraction for salmeterol, formoterol and salbutamol have been compared in the guinea pig isolated trachea. In addition, the possibility of inducing a non-beta adrenoceptor mediated relaxation by salmeterol was studied. METHODS--Concentration response experiments were conducted with isolated tracheal preparations (n = 4-6 in all experiments), precontracted by carbachol to cause either 40% (60 nmol/l), 80% (0.3 mumol/l) or 100% (3 mumol/l, supramaximal) of the maximum contraction. Each beta agonist was added cumulatively at each level of precontraction. Additional cumulative concentration response experiments were conducted for salmeterol alone at the highest level of precontraction, with and without beta blockade by sotalol (1 mmol/l). With the drug concentrations which produced the maximum response and the highest level of precontraction, the relaxation of formoterol (10 nmol/l) and salmeterol (1 mumol/l) was also compared non-cumulatively. Finally, with the corresponding drug concentrations and precontraction, the relaxant effect was compared for formoterol (10 nmol/l) in salmeterol relaxed airways with that of salmeterol (1 mumol/l) in formoterol relaxed airways. RESULTS--The increase in carbachol concentration from 60 nmol/l to 3 mumol/l induced a rightward shift in the mean (SE) concentration (log steps) causing 50% maximum relaxation for salmeterol (0.73 (0.17)), formoterol (0.85 (0.18)), and salbutamol (1.13 (0.11)). Significant differences in the maximum relaxant effect were shown at the highest level of precontraction only, with a remaining active tension of percentage precontraction of 27% (4%) for 1 mumol/l salbutamol and 35% (3%) for 10 nmol/l formoterol compared with 50% (2%) for 1 mumol/l salmeterol. The rank order of potency was: formoterol > salbutamol approximately salmeterol at all levels of precontraction (-log EC50: 9.32 (0.05) for formoterol, 7.82 (0.08) for salbutamol, and 7.50 (0.13) for salmeterol at 80% maximum precontraction). Beta blockade by sotalol (1 mmol/l) significantly inhibited the relaxation induced by salmeterol (1 mumol/l) (remaining active tension: 104% (1%) v 71% (11%) of precontraction) but not the relaxation induced by salmeterol (10 mumol/l) (remaining active tension: 75% (5%) v 71% (12%) of precontraction). In the non-cumulative experiments, formoterol displayed more relaxant effect than salmeterol (remaining active tension: 51% (6%) v 65% (6%) of precontraction). Finally, formoterol significantly relaxed salmeterol relaxed airways (relaxant effect: 22% (8%) of precontraction) whereas there was no significant response to salmeterol in formoterol relaxed airways (relaxant effect: 5% (12%) of precontraction). CONCLUSIONS--In the guinea pig isolated trachea, formoterol and salbutamol produce more relaxant effect than salmeterol, suggesting that salmeterol is a partial beta 2 agonist. Very high concentrations of salmeterol may induce non-beta adrenoceptor mediated relaxation. Formoterol is more potent than both salbutamol and salmeterol. There is no pronounced difference in the magnitude of antagonism against carbachol induced contractions between salmeterol, formoterol, and salbutamol.     

Tetrodotoxin does not block the epithelium-dependent release of prostaglandin E2 induced by electrical field stimulation in isolated ferret trachea

Electrical field stimulation (EFS) has previously been shown to induce the release of prostaglandin (PG) E2 from ferret tracheal epithelium. We have now conducted a study to see whether this effect of EFS is due to the activation of nerves or whether it is a non-neural effect. The release of PGE2 and 6-keto-PGF1 alpha into the bath fluid was assayed in isolated ferret tracheas with (E+) or without (E-) epithelium, stimulated by either EFS or direct vagal nerve stimulation (DNS) repeatedly for 120 min. EFS-stimulated E+ preparations showed a gradual decline in the contractile responses (30 +/- 1% of baseline) and an increase in PGE2 to 296 +/- 38 pg/ml. In EFS-stimulated, epithelium-denuded (E-) preparations, the decline was significantly lower (11 +/- 5%), as well as the final concentration of PGE2 (107 +/- 21 pg/ml). In DNS-stimulated E+ preparations, the contraction decline was 8 +/- 1% and the final concentration of PGE2 was less than 6 pg/ml. Although tetrodotoxin (TTX) abolished the contractile response in EFS-stimulated E+ preparations, it did not significantly reduce the release of PGE2 (260 +/- 6 pg/ml), whereas atropine partly counteracted the release. The bath concentration of 6-keto-PGF1 alpha increased, independently of the electrical stimulation, contractile response, or presence of the epithelium. We conclude that EFS activates the epithelium-dependent release of PGE2 by a TTX-resistant mechanism. This may be due to an activation of TTX-resistant nerves, or possibly to a non-neural effect, such as a direct effect on the epithelial cells. The results indicate that the airway epithelium has the ability to respond to certain stimuli with a pronounced release of PGE2, thereby counteracting bronchoconstriction.     

Mucosal inhibition of cholinergic contractions in ferret trachea can be transferred between organ baths

The influence of the mucosa on the contractile responses to cholinergic nerve stimulation in an in vitro nerve muscle preparation of ferret trachea was studied. Repeated contractions were induced by alternating direct vagal nerve stimulation (DNS) and electrical field stimulation (EFS). With intact mucosa there was a marked successive decrease of the contractile responses. During 60 minutes the responses decreased to 46 +/- 8% of baseline (Mean +/- SEM, n = 6), compared to 86 +/- 2% in preparations, in which the mucosa was initially removed. The mucosa dependent inhibition could be partly blocked by indomethacin (10 microM). The inhibitory effect could be transferred via the bath fluid from a donor preparation with intact mucosa to a recipient preparation with removed mucosa. Fluid transferred from a donor preparation with removed mucosa or from indomethacin treated preparations did not affect the contractile responses in the recipient preparation. We conclude that ferret tracheal mucosa can release a factor which inhibits the contractile responses to cholinergic nerve stimulation. The release of this factor can be blocked to a major part by indomethacin and the factor can be transferred from a donor to a recipient preparation.     

Sensitivity to sensitins and tuberculin in Swedish children. II. A study of preschool children

Non-BCG-vaccinated preschool children (4 or 5 years of age) were simultaneously tested on separate arms with a 2 IU PPD RT23 and 0.1 microgram Mycobacterium avium sensitin RS10 or 0.1 microgram Mycobacterium scrofulaceum sensitin RS95. None of the 762 children had any known exposure to tuberculosis. A total of 8.8% reacted with an induration (greater than or equal to 3 mm to PPD RT23 while 2% reacted with greater than or equal to 6 mm. Half the children were tested with M. avium sensitin: 18.9 and 7.8% reacted when 3 and 6 mm cut-off points, respectively, were taken. The remaining children were tested with M. scrofulaceum sensitin: 18.4 and 6.3%, respectively, reacted. In a previous study of schoolchildren aged 8 or 9 years, reactions to sensitins were considerably more frequent. Thus, sensitisation by atypical mycobacteria seems to increase from the preschool to the early school age. This finding probably reflects a continuous exposure of the children to atypical mycobacteria from various sources. The preschool children with a reaction to PPD RT23 greater than or equal to 6 mm were examined and chest X-rays were performed. All children were healthy but one child had enlarged lymph nodes in the mediastinum and abdomen. It cannot be excluded that these pathological findings were caused by atypical mycobacteria.     

Palpable lymph nodes of the neck in Swedish schoolchildren

We studied 3592 Swedish schoolchildren, 8 or 9 years old, examined for palpable submandibular, cervical and supraclavicular lymph nodes. All children were skin tested with 2 TU PPD RT23 and with 0.1 μ g of Mycobacterium avium sensitin or 0.1 μ g of M. scrofulaceum sensitin. A total of 991 children had palpable lymph nodes in any of the three locations. Among them, 811 had lymph nodes in one location, 162 in two locations and 18 in three. In 312 children, the lymph nodes were ± 5 mm in size in any location. The most common location was submandibular. Boys had a significantly higher prevalence of palpable lymph nodes than girls. There was also seasonal variation. Children infected by atypical mycobacteria (sensitin reaction ±6 mm) did not have a higher prevalence of palpable lymph nodes than those not infected.     

Bronchomotor tone and the slope of phase III of the N2-test

To determine the influence of bronchomotor tone on the slope of phase III of the N2-test, we studied subjects with reversible airflow limitation, who inhaled a standard dose of salbutamol. The design of the study allowed separation and comparison of the effects on the slope of phase III of changes in bronchomotor tone and in preinspiratory volume. The study shows that in subjects with a substantial reversibility of airflow limitation changes in the slope of phase III induced by salbutamol are related more to a change in preinspiratory volume than to a change in bronchomotor tone per se.