Role of 5-HT2 receptors family in the allergy-induced increased aorta contractile responses to 5-HT.

Asthma poses an increased risk for cardiovascular disorders, suggesting that allergy, which is an underlying process in asthma, causes atypical functioning of organs other than lungs. In a previous study in a guinea pig asthma model, we concluded that allergic sensitization increased aorta contractile responses to 5-HT. To further characterize these responses, here we explored the role of the 5-HT2 receptors family. We found that TCB-2 (5-HT2A agonist) and WAY161503 (5-HT2C agonist) induced aorta contractions resembling those elicited by 5-HT but less intense (~43 % and ~25 %, respectively). In these experiments, aortas from sensitized guinea pigs showed increased contractions to TCB-2, but not to WAY161503. In turn, MDL 100907 (5-HT2A antagonist) and RS-102221 (5-HT2C antagonist) caused a notably and a mild reduction of the 5-HT-induced contractions, respectively, with no differences seen between sensitized and non-sensitized tissues. BW723C86 (5-HT2B agonist) did not induce contractile responses and RS-127445 (5-HT2B antagonist) did not modify the contractile responses to 5-HT. In non-sensitized aortas, the pattern of protein expression of receptors was 5HT2B>5-HT2A=5-HT2C, which did not change in sensitized animals. In conclusion, we found that allergic sensitization increased the aorta contractile responses to 5-HT, partly mediated by enhanced responses of 5-HT2A receptors, which was unrelated to changes in the expression of these receptors.

Allergic sensitization increases contractile responses to 5-HT in guinea pig aorta.

Epidemiological and clinical studies suggest that asthma is associated with adverse cardiovascular outcomes, but its mechanism is uncertain. 5-Hydroxytryptamine (5-HT) is a mediator involved in asthma and in cardiovascular functioning. Thus, in the present study, we explored whether allergic sensitization in guinea pigs modifies 5-HT-induced contractile responses and 5-HT2A receptor expression in thoracic aorta rings. We found that sensitization produced a significant increase of 100 microM 5-HT-induced contractions of aorta rings (~27 % greater contraction than in non-sensitized animals, p<0.05). Preincubation with 10 nM ketanserin (a 5-HT2A receptor antagonist) reduced by ~30 % (p=0.003) and ~36 % (p=0.005) the area under the curve of 5-HT-induced contractions in aortas from non-sensitized and sensitized animals, respectively. There were no differences between sensitized and non-sensitized animals with respect to mRNA (qPCR) and protein (Western blot) expression of 5-HT2A receptor in thoracic aortas. We concluded that in this guinea pig model of asthma, allergic sensitization is not confined to airways, but also affects arterial contractile responses to 5-HT; changes in the expression of the 5-HT2A receptor appear not to be involved in this phenomenon.

Input respiratory impedance in mice: comparison between the flow-based and the wavetube method to perform the forced oscillation technique.

Objective and approach: In this study, we estimated the constant phase model (CPM) parameters from the respiratory impedance of male BALB/c mice by performing the forced oscillation technique (FOT) in a control group (n = 8) and in a murine model of asthma (OVA) (n = 10). Then, we compared the results obtained by two different methods, using a commercial equipment (flexiVent-flexiWare 7.X; SCIREQ, Montreal, Canada) (FXV) and a wavetube method equipment (Sly et al 2003 J. Appl. Physiol. 94 1460-6) (WVT). We believe that the results from different methods may not be comparable. First, we compared the results performing a two-way analysis of variance (ANOVA) for the resistance, elastance and tissue damping. MAIN RESULTS: We found statistically significant differences in all CPM parameters, except for resistance, when comparing Control and OVA groups. When comparing devices, we found statistically significant differences in resistance, while differences in elastance were not observed. For tissue damping, the results from WVT were observed to be higher than those from FXV. Finally, when comparing the relative variation between the CPM parameters of the Control and OVA groups in both devices, no significant differences were observed for all parameters. SIGNIFICANCE: We then conclude that this assessment can compensate the effect of using different cannulas. Furthermore, tissue damping differences between groups can be compensated, since bronchoconstrictors were not used. Therefore, we believe that relative variations in the results between groups can be a comparing parameter when using different equipment without bronchoconstrictor administration.

Bacterial extract (OM-85) with human-equivalent doses does not inhibit the development of asthma in a murine model.

BACKGROUND: OM-85 is an immunostimulant bacterial lysate, which has been proven effective in reducing the number of lower airways infections. We investigated the efficacy of the bacterial lysate OM-85 in the primary prevention of a murine model of asthma. METHODS: In the first phase of our study the animals received doses of 0.5µg, 5µg and 50µg of OM-85 through gavage for five days (days -10 to -6 of the protocol), 10 days prior to starting the sensitisation with ovalbumin (OVA), in order to evaluate the results of dose-response protocols. A single dose (5µg) was then chosen in order to verify in detail the effect of OM-85 on the pulmonary allergic response. Total/differential cells count and cytokine levels (IL-4, IL-5, IL-13 and IFN-γ) from bronchoalveolar lavage fluid (BALF), OVA-specific IgE levels from serum, lung function and lung histopathological analysis were evaluated. RESULTS: OM-85 did not reduce pulmonary eosinophilic response, regardless of the dose used. In the phase protocol using 5µg/animal of OM-85, no difference was shown among the groups studied, including total cell and eosinophil counts in BALF, serum OVA-specific IgE, lung histopathologic findings and lung resistance. However, OM-85 decreased IL-5 and IL-13 levels in BALF. CONCLUSIONS: OM-85, administered in early life in mice in human-equivalent doses, does not inhibit the development of allergic pulmonary response in mice.

Decreased expression of ectonucleotidase E-NPP1 in leukocytes from subjects with severe asthma exacerbation.

Several studies suggest that ATP and related nucleotides play a role in the pathophysiology of asthma. However, the functionality of ectonucleotidases in this disease has been scantly investigated. We studied total ectonucleotidase activity in leukocytes from patients suffering from asthma exacerbation and explored the expression of E-NTPDase 1, 2, 3, and 8, and E-NPP1, 2, and 3, in their polymorphonuclear cells by immunofluorescence and qPCR. Leukocytes from patients with mild or moderate asthma exacerbation had similar ectonucleotidase activity than leukocytes from healthy subjects, while in patients with severe asthma exacerbation, this activity was lower. Of the ectonucleotidases studied, only E-NPP1 displayed diminished immunofluorescence and a significant decrease in its mRNA expression, both in patients with severe asthma exacerbation. This reduced E-NPP1 expression could be responsible for increased amounts of ATP or other nucleotides, capable of worsening asthma exacerbation, and warranting further investigation.

5-HT Receptor Antagonism Attenuates the Ischemia-Reperfusion Injury After Rabbit Lung Preservation.

The success of lung transplantation is threatened by the appearance of ischemia-reperfusion injury, which is characterized by increased vascular permeability. 5-Hydroxytryptamine (5-HT; serotonin) is known to produce microvascular leakage in the systemic circulation, but its possible role in ischemia-reperfusion injury after lung preservation has not been reported. In this work we measured the release of 5-HT during a 24-hour rabbit lung preservation, and the effect of methiothepin (antagonist of the majority of 5-HT receptors) and SB204741 (antagonist of 5-HT2B/2C receptors) on the modified capillary filtration coefficient (mKf,c) was evaluated at the end of this period. Our results showed that the highest release rate of 5-HT occurred during the first 15 minutes after the lung harvesting and progressively decreased in the following time intervals. The baseline mKf,c greatly increased after 24 hours of lung preservation, and this increment was partially reduced by methiothepin and even more by SB204741. We concluded that 5-HT may play an important role in the ischemia-reperfusion process after lung preservation.

Extracellular DNA traps in bronchoalveolar fluid from a murine eosinophilic pulmonary response.

Asthma is associated with a loss of the structural integrity of airway epithelium and dysfunction of the physical barrier, which protects airways from external harmful factors. Granulocyte activation causes the formation of extracellular traps, releasing web-like structures of DNA and proteins, being important to kill pathogens extracellularly. We investigated whether eosinophils infiltrating airways in an experimental model of asthma would induce eosinophil extracellular traps (EETs) in bronchoalveolar lavage fluid and lung tissue. We showed that an ovalbumin (OVA) asthma protocol presented a significant increase in eosinophil counts with increased extracellular DNA in bronchoalveolar lavage fluid as well as in lung tissue, confirming the presence of DNA traps colocalized with eosinophil peroxidase. EETs formation was reversed by DNase treatment. With these approaches, we demonstrated for the first time that OVA-challenged mice release extracellular DNA traps, which could aggravate pulmonary dysfunction.

Inhibition of extracellular nucleotides hydrolysis intensifies the allergic bronchospasm. A novel protective role of ectonucleotidases.

BACKGROUND: Nucleotides released to the extracellular space stimulate purinergic receptors, and their effects are modulated by ectonucleotidases. The role of ATP in the allergic bronchospasm has been scantly studied. METHODS: We used several techniques (plethysmography, organ baths, confocal microscopy, RT-PCR, ATP measurement) to explore the role of nucleotides and ectonucleotidases in the allergic bronchospasm in guinea pigs. RESULTS: While allergenic challenge with a low-dose ovalbumin (OVA) only produced a small bronchospasm (~2-fold the basal lung resistance), previous inhibition of ectonucleotidases by ARL-67156 greatly intensified this response (~11-fold the basal lung resistance, with 44% mortality). Bronchoalveolar lavage fluid obtained during this bronchospasm contained increased ATP concentration. This potentiation was abolished by antagonism of purinergic receptors (suramin+RB2) or TXA2 receptor (SQ29548), or by intratracheal apyrase. In tracheal rings and lung parenchyma strips, OVA caused a concentration-dependent contraction. Suramin+RB2 or levamisole produced a significant rightward displacement of this response, and ARL-67156 did not modify it. Platelets stimulated with OVA released ATP. Confocal images of nonsensitized tracheas showed slight fluorescence for P2Y6 receptors in epithelium and none for P2Y4 . Sensitized animals showed strong fluorescence to both receptors and to alkaline phosphatase in the airway epithelium. This correlated with a large increment in mRNA for P2Y4 and P2Y6 receptors in sensitized animals. CONCLUSIONS: Nucleotides greatly potentiate the allergic bronchospasm when ectonucleotidases activity is diminished, and this effect is probably favored by the upregulation of P2Y4 and P2Y6 receptors in airway epithelium during sensitization. These results prompt for further research on these mechanisms in human asthma.

Drug resistance beyond extensively drug-resistant tuberculosis: individual patient data meta-analysis.

The broadest pattern of tuberculosis (TB) drug resistance for which a consensus definition exists is extensively drug-resistant (XDR)-TB. It is not known if additional drug resistance portends worsened patient outcomes. This study compares treatment outcomes of XDR-TB patients with and without additional resistance in order to explore the need for a new definition. Individual patient data on XDR-TB outcomes were included in a meta-analysis comparing outcomes between XDR alone and three nonmutually exclusive XDR-TB patient groups: XDR plus resistance to all the second-line injectables (sli) and capreomycin and kanamycin/amikacin (XDR+2sli) XDR plus resistance to second-line injectables and to more than one group 4 drug, i.e. ethionamide/protionamide, cycloserine/terizidone or para-aminosalicylic acid (XDR+sliG4) and XDR+sliG4 plus resistance to ethambutol and/or pyrazinamide (XDR+sliG4EZ). Of 405 XDR-TB cases, 301 were XDR alone, 68 XDR+2sli, 48 XDR+sliG4 and 42 XDR+sliG4EZ. In multivariate analysis, the odds of cure were significantly lower in XDR+2sli (adjusted OR 0.4, 95% CI 0.2-0.8) compared to XDR alone, while odds of failure and death were higher in all XDR patients with additional resistance (adjusted OR 2.6-2.8). Patients with additional resistance beyond XDR-TB showed poorer outcomes. Limitations in availability, accuracy and reproducibility of current drug susceptibility testing methods preclude the adoption of a useful definition beyond the one currently used for XDR-TB.

Role of 5-HT2A, 5-HT4 and 5-HT7 receptors in the antigen-induced airway hyperresponsiveness in guinea-pigs.

BACKGROUND: A possible role of 5-hydroxytryptamine (5-HT) in the origin of antigen-induced airway hyperresponsiveness (AI-AHR) has been scarcely investigated. OBJECTIVE: To explore the participation of different 5-HT receptors in the development of AI-AHR in guinea-pigs. METHODS: Lung resistance was measured in anaesthetized guinea-pigs sensitized to ovalbumin (OVA). Dose-response curves to intravenous (i.v.) acetylcholine (ACh) were performed before and 1 h after antigenic challenge and expressed as the 200% provocative dose (PD(200)). Organ bath experiments, confocal microscopy and RT-PCR were additionally used. The 5-HT content in lung homogenates was measured by HPLC. RESULTS: Antigenic challenge significantly decreased PD(200), indicating the development of AI-AHR. This hyperresponsiveness was abolished by a combination of methiothepin (5-HT(1)/5-HT(2)/5-HT(5)/5-HT(6)/5-HT(7) receptors antagonist) and tropisetron (5-HT(3)/5-HT(4) antagonist). Other 5-HT receptor antagonists showed three different patterns of response. Firstly, WAY100135 (5-HT(1A) antagonist) and ondansetron (5-HT(3) antagonist) did not modify the AI-AHR. Secondly, SB269970 (5-HT(7) antagonist), GR113808 (5-HT(4) antagonist), tropisetron or methiothepin abolished the AI-AHR. Thirdly, ketanserin (5-HT(2A) antagonist) produced airway hyporresponsiveness. Animals with bilateral vagotomy did not develop AI-AHR. Experiments in tracheal rings showed that pre-incubation with LP44 or cisapride (agonists of 5-HT(7) and 5-HT(4) receptors, respectively) induced a significant increase of the cholinergic contractile response to the electrical field stimulation. In sensitized lung parenchyma strips, ketanserin diminished the contractile responses to ACh. Sensitization was associated with a ninefold increase in the 5-HT content of lung homogenates. Confocal microscopy showed that sensitization enhanced the immunolabelling and co-localization of nicotinic receptor and 5-HT in airway epithelium, probably located in pulmonary neuroendocrine cells (PNECs). RT-PCR demonstrated that neither sensitization nor antigen challenge modified the 5-HT(2A) receptor mRNA levels. CONCLUSIONS: Our results suggested that 5-HT was involved in the development of AI-AHR to ACh in guinea-pigs. Specifically, 5-HT(2A), 5-HT(4) and 5-HT(7) receptors seem to be particularly involved in this phenomenon. Participation of 5-HT might probably be favoured by the enhancement of the PNECs 5-HT content observed after sensitization.

Beta1-integrins shedding in a guinea-pig model of chronic asthma with remodelled airways.

BACKGROUND: A hallmark of airway remodelling in asthma is subepithelial fibrosis, but its relation with airway dysfunction is still controversial. OBJECTIVE: To describe airway functional abnormalities and subepithelial remodelling induced by repetitive antigenic challenges. METHODS: Nine inhaled antigenic challenges were applied every 10 days to guinea-pigs sensitized to ovalbumin (OVA). Antigen-induced airway hyperresponsiveness (AI-AHR) to histamine and its immunohistopathological relationship was evaluated at the first, third and ninth OVA challenges. RESULTS: From the first challenge on, OVA induced acute transient bronchoobstruction followed by development of AI-AHR. A progressive rise in baseline Penh (a bronchoobstruction index) and granulocyte airway infiltration was also observed. After the ninth OVA challenge, the amount of extracellular matrix in the subepithelial region (SER) of bronchi and bronchioles was increased. Immunohistochemistry analysis showed that this SER fibrosis was associated to beta1-integrin subunit overexpression, even in acellular areas. Immunoelectronmicroscopy corroborated the location of beta1-integrin in extracellular matrix, essentially in types l and II collagen fibres. Presence of alpha1- and alpha2-integrin subunits in these areas was also corroborated. AI-AHR was correlated with degree of SER increment, cell infiltration, and beta1-integrin expression. CONCLUSION: Our data suggested that beta1-integrin shedding produced by repetitive allergen challenges in guinea-pigs was associated with collagen deposition in SER of bronchi and bronchioles, along with inflammatory cells infiltration and AI-AHR development.

Guidelines for diagnosing and treating pulmonary infiltrates in children with acute leukaemia: impact of timely decisions.

AIM: Children with leukaemia are at increased risk of pulmonary complications, often with unspecific clinical data, delayed diagnosis and a high mortality rate. We evaluated the usefulness of diagnostic-therapeutic guidelines (DTG) in which specific times for decision making were incorporated. METHODS: Clinical charts of children with acute leukaemia and suspicion of pulmonary involvement were reviewed. Patients were allocated to group I if their diagnostic and therapeutic decisions were in accordance with the DTG, and to group II if not. RESULTS: Children from group I (n=32) and group II (n=28) did not differ with respect to age (9.3+/-0.5 years old, mean+/-SEM), gender, type, risk and stage of leukaemia, anaemia and neutropenia. Total length of hospital stay and hospitalization due to the pulmonary disease were shorter in group I than in group II (14.8+/-2.1 vs. 28.5+/-3.7 days, p=0.0016; and 10.8+/-1.0 vs. 18.4+/-1.8 days, p=0.0003, respectively). Two patients (6.3%) died due to the pulmonary pathology in group I, and nine (32.1%, p=0.016) in group II. CONCLUSIONS: Diagnostic-therapeutic guidelines that incorporate timely decisions constitute a useful algorithm to reduce the length of hospital stay and mortality in children with acute leukaemia and pulmonary infiltrates. A prospective study is needed to validate these results.

Effect of altitude on the frequency of pulmonary tuberculosis.

SETTING: Pulmonary tuberculosis (PTB) incidence greatly varies around the world, a phenomenon usually attributed to socio-economic factors or health service availability. A recent study, however, indicated that PTB was inversely related to altitude. OBJECTIVE: To evaluate factors associated with PTB notification rates in Mexico. METHODS: Annual notification rates (1998-2002) of PTB in each of the 32 Mexican states were analysed, and likely factors were assessed through correlation and multiple regression analyses. RESULTS: Most variables lacked association with PTB rates, including percentage of population aged > or = 65 years, population density, percentage of population with < or = 2 minimum salaries, percentage of population with social security, level of education, diabetes incidence, percentage of immigration, percentage of rural population and a global marginalisation index. Only altitude above sea level correlated with tuberculosis incidence (r = -0.74, P < 0.0001). Likewise, in the multiple regression analysis only altitude reached a statistically significant association. CONCLUSION: Our results showed that altitude had a strong inverse relationship to PTB notification rates in Mexico, which might be related to the well known changes in alveolar oxygen pressure at different altitudes. Interestingly, several factors traditionally considered as predisposing conditions for the development of PTB did not correlate with the disease.

[Bronchial nodules produced by Strongyloides stercoralis as the cause of bronchial obstruction]. / Nódulos bronquiales producidos por Strongyloides stercoralis como causa de obstrucción bronquial.

Infection by Strongyloides stercoralis can cause asthma-like symptoms through mechanisms that have not yet been clarified. A 55-year-old male farm worker with a 2-year history of illness diagnosed as asthma and treated unsuccessfully with bronchodilators and corticosteroids was referred to our hospital with severe dyspnea. The initial chest radiograph showed mild air trapping, and pulmonary function tests detected airway obstruction that did not respond to salbutamol. Bronchoscopy revealed multiple nodules protruding into the airway lumen. S. stercoralis larvae were detected in bronchoalveolar lavage fluid and stool samples. Although treatment with albendazole was initiated, the patient's condition worsened over the next 3 days, hemoptysis presented, and the process ended in death. Autopsy demonstrated Strongyloides larvae in the bronchial nodules. Infection by S. stercoralis should be considered in the differential diagnosis of asthmatic-like symptoms refractory to treatment. In such cases nodules may be responsible for obstruction.

Diabetes modifies the male:female ratio in pulmonary tuberculosis.

SETTING: Socio-cultural factors have been invoked to explain the male predominance among patients with pulmonary tuberculosis, but there is no conclusive evidence of their role. OBJECTIVE: To assess male predominance in a group of diabetics with pulmonary tuberculosis compared with patients with pulmonary tuberculosis alone. DESIGN: Clinical records of in-patients with pulmonary tuberculosis and with (TBDM group, n = 202) or without (TB group, n = 226) diabetes mellitus were reviewed, and the male percentages in each of six age groups (15-29, 30-39, 40-49, 50-59, 60-69, > or = 70 years) calculated. RESULTS: In the TB group, no gender difference (51% males) was found in the first age period, followed by a male predominance thereafter (71%, 68%, 75%, 63% and 58%). The TBDM group showed a similar pattern in the first two age groups (56% and 74%), followed by a steadily decline (r(S) = -0.90, P = 0.04) in male percentage (60%, 44%, 45%, 27%), leading to a female predominance after age 50. The association of age and gender was also corroborated by logistic regression in TBDM (P = 0.02), but not in TB (P = 0.19) patients. CONCLUSIONS: Diabetes was associated with a progressive shift of male predominance in pulmonary tuberculosis. Because diabetes is a disease that affects social activities similarly in men and women, our results suggest that factors other than socio-cultural ones are also important for determining the male predominance in pulmonary tuberculosis.

Main diagnosis and cause of death in a neonatal intensive care unit: do clinicians and pathologists agree?

AIM: To determine the agreement rates between clinical and autopsy diagnoses in a neonatal intensive care unit (NICU), distinguishing between the main diagnosis and cause of death. METHODS: Clinical and autopsy records of 75 infants who died in two consecutive years in the NICU (autopsy rate 42.6%) of a pediatric hospital in Mexico City were reviewed. RESULTS: Ninety-two percent of main clinical diagnoses were confirmed by autopsy. Four conditions (congenital cardiopathy, prematurity, specific congenital syndromes and hyaline membrane disease) accounted for more than two-thirds of diagnoses. However, for cause of death, the global agreement was only 50%. The most common conditions considered by clinicians (77%) and pathologists (56%) to be the causes of death were cardiogenic, septic or mixed shocks. Additionally, clinicians omitted 34 relevant conditions in 30 (40.0%) patients, and 21 of these conditions possibly played a role in the deaths of 17 (22.7%) patients. The most frequently omitted diagnosis was pneumonia, in 9 (26.5%) patients. Omissions were not related to gestational age, age at death, days as an inpatient, or gender. CONCLUSION: Despite a high agreement rate in the main diagnoses, notable imprecisions were present regarding cause of death and antemortem overlooking of potentially fatal conditions, confirming the useful role of autopsy to verify clinical diagnoses and suggesting that differentiation between the main diagnosis and cause of death should be carried out in future studies.

Results of a 12-month regimen for drug-resistant pulmonary tuberculosis.

SETTING: Several therapeutic regimens for drug-resistant tuberculosis have been suggested, most of them with a total duration of 18-24 months. OBJECTIVE: To report our experience using a shorter regimen. DESIGN: Fifty patients with drug-resistant pulmonary tuberculosis were managed by withdrawing all anti-tuberculosis drugs until the results of a drug sensitivity test were obtained (approximately 3 months), and then a 12-month self-administered regimen with four to six anti-tuberculosis drugs at full daily doses was initiated, based primarily on the sensitivity test and secondarily on the history of previous treatment. RESULTS: In 31 patients treatment was completed as planned, in six it was irregular and 13 definitively abandoned it. In the best scenario, 90.3% (28/31) of patients with full treatment were cured; this outcome was similar for both multidrug-resistant (MDR, n = 18, 88.9%) and non-MDR (n = 13, 92.3%) patients. Six months later, the relapse rate was 4.8%, and after a 5-year follow-up 14 out of 18 cured patients who were located remained asymptomatic (77.8%). If the worst scenario was applied, a 62.0% cure rate (31/50) was obtained. CONCLUSIONS: A 12-month regimen with a minimum of four anti-tuberculosis agents at full dose, essentially selected on drug sensitivity testing, could be an alternative option for the treatment of drug-resistant pulmonary tuberculosis.

[Prevalence of asthma in schoolchildren from the Mexican city Hermosillo]. / Prevalencia de asma en niños escolares de la ciudad mexicana de Hermosillo.

Asthma is a very common disease, but its prevalence greatly varies from region to region, even in the same country. In the northwest of Mexico there is a lack of epidemiological studies on this disease. In this work a standardized questionnaire (ISAAC) was applied to parents of children attending 8 primary schools in the Mexican city of Hermosillo, Sonora. Of 3000 questionnaires sent, 1489 (49%) were acceptably answered. Children were of either sex and 9.1 +/- 1.8 years old (mean +/- SD). From this population, 74 (10.4%) out of 713 male and 67 (8.6%) out of 776 female children had an affirmative response to que question "Have you ever had asthma?", from which we conclude that global prevalence of asthma in the studied sample was 9.5%, an intermediate figure among those reported from other studies performed in Mexico.

Differences between inhaled and intravenous bronchial challenge to detect O(3)-induced hyperresponsiveness.

Ozone (O(3))-induced airway hyperresponsiveness in laboratory animals is usually demonstrated through dose-response curves with inhaled or intravenous bronchoconstrictor agonists. However, comparability of these two routes has not been well documented. Thus guinea pig airway responsiveness to ACh and histamine was evaluated 16-18 h after O(3) (3 parts/million, 1 h) or air exposure by two plethysmographic methods (spontaneously breathing and mechanically ventilated) and by two administration routes (inhalatory or intravenous). We found that O(3) caused airway hyperresponsiveness to intravenous, but not to inhaled, agonists, independent of the plethysmographic method used. Suitability of the inhalatory route to detect airway hyperresponsiveness was corroborated with inhaled ACh after an antigen challenge or extending O(3) exposure to 3 h. Acetylcholinesterase activity was not modified after O(3) exposure in lung homogenates and blood samples. Thus inhaled agonists were less effective to reveal the airway hyperresponsiveness after an acute O(3) exposure than intravenous ones, at least for the 1-h exposure to 3 parts/million, and this difference seems not to be related to an O(3)-induced inhibition of the acetylcholinesterase activity.