Bosentan inhibits cigarette smoke-induced endothelin receptor expression in pulmonary arteries.

The endothelin (ET) system contributes to lung vascular tension and remodelling in smokers and chronic obstructive pulmonary disease (COPD) patients. This study examined the effect of cigarette smoke (CS) on ET receptor A (ET(A)) and B (ET(B)) expression in human pulmonary artery smooth muscle cells (HPASMCs) and human small intrapulmonary arteries, as well as their functional consequences. CS extract (CSE) increased ET(A) and ET(B) expression in HPASMCs and small intrapulmonary arteries, which was attenuated by bosentan, the ET(A) antagonist BQ123 and the ET(B) antagonist BQ788, and by blocking ET-1 with a monoclonal antibody against ET-1, suggesting a feed-forward mechanism mediated by ET-1 release. ET receptor (ETR) antagonism attenuated the CSE-induced HPASMC proliferation. Furthermore, CSE exposure increased the acute ET-1-induced small intrapulmonary artery contraction, which was attenuated by bosentan, BQ123 and BQ788. Pulmonary arteries from smokers and COPD patients showed a higher expression of ET(A) and ET(B) than those of nonsmoker patients. These results show a novel mechanism by which ETR blockade attenuates CS-induced ETR overexpression and, subsequently, small intrapulmonary artery tension. These data may be of potential value to explain therapeutic effects of bosentan in some forms of disproportionate pulmonary hypertension in COPD patients.

Validity of insertion depth measurement in double-balloon endoscopy.

BACKGROUND AND STUDY AIMS: In double-balloon enteroscopy (DBE) the use of a reliable and practical method to calculate the insertion depth of the endoscope could help to improve diagnosis accuracy and optimize the effort and cost of the technique. The objectives of this work were to compare and evaluate two methods of estimating the insertion depth and to obtain a descriptive model capable of representing the exploration dynamics and efficiency in terms of advanced distance and time. METHODS: Oral DBE was performed in 25 pigs. Insertion depth was calculated during the procedure by: 1) estimation of time and distance for each push and pull cycle during progression; and 2) estimation of distance during withdrawal. At the maximum insertion depth a tattoo was placed, and the observed measures for the two methods were compared with the distance between the pylorus and the mark after euthanasia and necropsy of the animals 1 week after DBE. RESULTS: The average insertion depth during progression, withdrawal, and after necropsy was 324.92 cm, 317.23 cm, and 342.05 cm, respectively (P Anova = 0.72). The Pearson correlation coefficient (r > 0.85; P < 0.001) and paired Brand - Altman plots demonstrated high agreement between progression and necropsy (0.03 % difference) and between withdrawal and necropsy (6.9 % difference). The exploration dynamics and efficiency in terms of advanced distance per cycle and time fitted to potential and logarithmic regression models, respectively. CONCLUSIONS: Measurement of insertion depth in vivo was validated in the porcine model during progression and withdrawal. Estimation during progression was more accurate and allowed exploration dynamics and efficiency to be plotted, which might be used as approximate reference values for humans.

Aclidinium inhibits cholinergic and tobacco smoke-induced MUC5AC in human airways.

Mucus hypersecretion and mucin MUC5AC overexpression are pathological features of chronic obstructive pulmonary disease (COPD). This study examines the inhibitory effect of aclidinium, a new long-acting muscarinic antagonist, on MUC5AC expression in human airway epithelial cells. MUC5AC mRNA (RT-PCR) and protein expression (ELISA and immunohistochemistry) were studied in human bronchial tissue and differentiated human airway epithelial cells activated with carbachol (100 µM) or cigarette smoke extract in the absence or presence of aclidinium. Carbachol increased MUC5AC mRNA and protein expression in human bronchus and cultured epithelial cells. Aclidinium inhibited the carbachol-induced MUC5AC mRNA and protein expression with potency (half maximal inhibitory concentration) ~1 nM in human bronchus and cultured airway epithelial cells. AG1478, a selective inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, inhibited carbachol-induced MUC5AC responses, indicating EGFR transactivation. Aclidinium inhibited carbachol-induced phospho-EGFR and phospho-p44/42 MAPK expression. In cultured airway epithelial cells transfected with small interfering (si)RNA against muscarinic receptor subtypes, siRNA-M3 but not siRNA-M2 blocked carbachol-induced MUC5AC expression. Cigarette smoke-induced MUC5AC upregulation in cultured airway epithelial cells was suppressed by aclidinium. In conclusion, aclidinium decreases carbachol and tobacco smoke-induced MUC5AC overexpression in human airway epithelial cells. This effect may contribute to the clinical efficacy of aclidinium in mucus hypersecretory diseases including COPD.

Increased lung neutrophil apoptosis and inflammation resolution in nonresponding pneumonia.

Neutrophil activation state and its relationship with an inflammatory environment in community-acquired pneumonia (CAP) remain insufficiently elucidated. We aimed to evaluate the neutrophil apoptosis and cytokine pattern in CAP patients after 72 h of treatment, and their impact on infection resolution. Apoptosis of blood and bronchoalveolar lavage (BAL) neutrophils was measured in nonresponding CAP (NCAP), in responding CAP (blood only) and in patients without infection (control). Pro-inflammatory (interleukin (IL)-6, IL-8) and anti-inflammatory (IL-10) cytokines were measured. Main outcomes were clinical stability and days of hospitalisation. Basal neutrophil apoptosis was higher in the BAL and blood of NCAP, whereas spontaneous apoptosis (after 24 h culture) was lower. Cytokines in NCAP were higher than in responding CAP and control: IL-6 was increased in BAL and blood, IL-8 in BAL and IL-10 in blood. An increased basal apoptosis (≥20%) in BAL of NCAP was associated with lower systemic IL-10 (p<0.01), earlier clinical stability (p=0.05) and shorter hospital stay (p=0.02). A significant correlation was found for systemic IL-6 and IL-10 with days to reach stability and length of stay. After 72 h of treatment, an increased basal alveolar neutrophil apoptosis might contribute to downregulation of inflammation and to faster clinical stability.

Oxidative stress-induced glucocorticoid resistance is prevented by dual PDE3/PDE4 inhibition in human alveolar macrophages.

BACKGROUND: Oxidative stress is present in airway diseases such as severe asthma or Chronic Obstructive Pulmonary Disease and contributes to the low response to glucocorticoids through the down-regulation of histone deacetylase (HDAC) activity. OBJECTIVE: To study the effects of the phosphodiesterase (PDE)-3 and 4 inhibitors and their combination vs. glucocorticoids in a model of lipopolysaccharide (LPS)-induced cytokine release in alveolar macrophages under oxidative stress conditions. METHODS: Differentiated U937 or human alveolar macrophages were stimulated with H(2) O(2) (10-1000 µM) or cigarette smoke extract (CSE, 0-15%) for 4 h before LPS (0.5 µg/mL, 24 h) addition. In other experiments, cells were pre-treated with dexamethasone or budesonide (10(-9) -10(-6) M), with the PDE4 inhibitor rolipram (10(-9) -10(-5) M), PDE3 inhibitor motapizone (10 µM), 3',5'-cyclic monophosphate enhancer PGE(2) (10 nM), or with the combination of rolipram (10(-6) M)+PGE(2) (10 nM)+motapizone (10 µM) 15 min before oxidants. IL-8 and TNF-α were measured by ELISA and HDAC activity by a colorimetric assay. RESULTS: Budesonide and dexamethasone produced a concentration-dependent inhibition of the LPS-induced IL-8 and TNF-α secretion with an E(max) about 90% of inhibition, which was reduced by approximately 30% in the presence of H(2)O(2) or CSE. Pre-treatment with rolipram, motapizone or PGE2 only reached about 20% of inhibition but was not affected by oxidative stress. In contrast, PDE4/PDE3 combination in presence of PGE2 effectively inhibited the LPS-induced cytokine secretion by about 90% and was not affected by oxidative stress. Combined PDE4 and PDE3 inhibition reversed glucocorticoid resistance under oxidative stress conditions. HDAC activity was reduced in the presence of oxidative stress, and in contrast to glucocorticoids, pre-treatment with PDE4/PDE3 combination was able to prevent HDAC inactivity. CONCLUSIONS & CLINICAL RELEVANCE: This study shows that the combination of the PDE3/PDE4 inhibitors prevents alveolar macrophage activation in those situations of glucocorticoid resistance, which may be of potential interest to develop new effective anti-inflammatory drugs in airway diseases.

Haemodynamic effects of long-term administration of sildenafil in normotensive pregnant and non-pregnant rats.

OBJECTIVE: To determine the effects of chronic administration of sildenafil citrate on healthy pregnant rats. DESIGN: In vivo animal experimental study. SETTING: Fundación IVI-Instituto Universitario IVI, Valencia, Spain. SAMPLE: Pregnant and non-pregnant Wistar rats exposed to chronic administration of sildenafil. METHODS: Placental cross-barrier and feto-maternal relationship levels, maternal blood pressure, and haemodymamic effects on uterine arteries were evaluated. The effect of growth on weight and fetal tissues, and on perinatal outcome, was investigated. MAIN OUTCOME MEASURES: Maternal blood pressure, blood viscosity, vascular indices of uterine arteries and fetal ductus venosus, plasmatic levels of sildenafil, embryo/fetal and litter weights, perinatal/postnatal survival rates. RESULTS: Sildenafil citrate crossed the placenta. The maternal and fetal levels of sildenafil, and its metabolite desmethyl-sildenafil, demonstrated a positive linear correlation in treated pregnant animals versus controls; a selective maternal hypotensive effect without changes in uterine vascular resistance was noted on days E8 and E11 (embryonic day). The lower pulsatility index of the ductus venosus on day E18 suggests fetal overflow at the end of the pregnancy. Effects on offspring were placental and liver enlargement, and increased fetal weight gain in the second half of pregnancy (irrespective of liver enlargement) and at birth. Perinatal and postnatal survival rates in the sildenafil group remained unaltered. No haemodynamic effects were evident in non-pregnant animals. CONCLUSIONS: In normotensive rats, sildenafil appears to have a selective effect at the onset of pregnancy, implying increased fetal blood supply, and increased fetal weight, and placental and liver enlargement, but no increased perinatal mortality.

Taurine chloramine inhibits functional responses of human eosinophils in vitro.

BACKGROUND: Eosinophils are prominent effectors of allergic inflammation. Taurine-chloramine (TauCl), a derivative of the amino acid taurine, shows antioxidant properties in different cell systems but its effects on eosinophils have not been reported. OBJECTIVE: To study the effects of TauCl and taurine on functional responses of isolated human eosinophils activated by different stimuli. METHODS: Human eosinophils were purified from the blood of healthy donors by a magnetic bead separation system. The effects of TauCl and taurine (0.1-1 mM) were investigated on the generation of superoxide anion (ferricytochrome-c reduction microassay), calcium signal (fluorimetry), p47phox-p67phox translocation (Western blot), leukotriene C4 (LTC4) production (enzymeimmunoassay), eosinophil peroxidase (EPO) release (spectrophotometry), eosinophil cationic protein (ECP) release (radioimmunoassay), apoptosis (flow cytometry with annexin V-propidium iodide), and nuclear factor-kappaB (NF-kappaB) activation (Western blot). RESULTS: TauCl inhibited superoxide anion generation triggered by N-formyl-Met-Leu-Phe (fMLP; 30 nM), phorbol myristate acetate (1 nM) and serum opsonized zymosan (0.5 mg/mL) with similar potency (IC50 approximately 200 microM) for the three stimuli, while taurine (0.1-1 mM) was scarcely effective. TauCl but not taurine inhibited p47phox-p67phox translocation. TauCl (200 microM) and taurine (1 mM) did not modify the [Ca2+]i responses to fMLP. TauCl inhibited the release of EPO (IC50 approximately 200 microM) and reduced ECP and LTC4 production from fMLP-activated eosinophils while taurine was without significant effects. TauCl (1 mM) did not change constitutive apoptosis but significantly attenuated the ability of granulocyte-monocyte colony-stimulating factor (GM-CSF) and IL-5 to prevent apoptosis. The activation of eosinophil NF-kappaB induced by GM-CSF and IL-5 was suppressed by TauCl. CONCLUSION: Taurine is without significant in vitro effects on human eosinophil functions but its derivative TauCl inhibits oxidative burst and generation of inflammatory mediators, and reverses the survival effect produced by inflammatory cytokines. Therefore, endogenous TauCl may help to suppress excessive inflammatory response in eosinophils at inflammatory sites.

Roflumilast inhibits leukocyte-endothelial cell interactions, expression of adhesion molecules and microvascular permeability.

BACKGROUND AND PURPOSE: The present study addressed the effects of the investigational PDE4 inhibitor roflumilast on leukocyte-endothelial cell interactions and endothelial permeability in vivo and in vitro. EXPERIMENTAL APPROACH: In vivo, intravital video-microscopy was used to determine effects of roflumilast p.o. on leukocyte-endothelial cell interactions and microvascular permeability in rat mesenteric venules. In vitro, the effects of roflumilast N-oxide, the active metabolite of roflumilast in humans, and other PDE4 inhibitors on neutrophil adhesion to tumour necrosis factor alpha (TNFalpha)-activated human umbilical vein endothelial cells (HUVEC), E-selectin expression and thrombin-induced endothelial permeability was evaluated. Flow cytometry was used to determine the effect of roflumilast on N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced CD11b upregulation on human neutrophils. KEY RESULTS: In vivo, roflumilast, given 1 h before lipopolysaccharide (LPS), dose-dependently reduced leukocyte-endothelial cell interactions in rat mesenteric postcapillary venules. It also diminished histamine-induced microvascular permeability. Immunohistochemical analyses revealed that roflumilast prevented LPS-induced endothelial P- and E-selectin expression. In vitro, roflumilast N-oxide concentration-dependently suppressed neutrophil adhesion to TNFalpha-activated HUVEC and CD11b expression on fMLP-stimulated neutrophils. It also reduced TNFalpha-induced E-selectin expression on HUVEC, when PDE3 activity was blocked. HUVEC permeability elicited by thrombin was concentration-dependently suppressed by roflumilast N-oxide. While roflumilast N-oxide was as potent as roflumilast at inhibiting stimulated endothelial cell and neutrophil functions, both compounds were significantly more potent than the structurally unrelated PDE4 inhibitors, rolipram or cilomilast. CONCLUSIONS AND IMPLICATIONS: These findings further support earlier observations on the inhibition of inflammatory cell influx and protein extravasation by roflumilast in vivo.

Directly observed treatment for tuberculosis in pharmacies compared with self-administered therapy in Spain.

OBJECTIVES: To compare directly observed treatment (DOT) of tuberculosis through pharmacy offices with self-administered treatment (SAT) in patients at risk for non-adherence. METHODS: Prospective study for DOT (1999-2002) and retrospective study for SAT (1996-1998) in patients at risk for non-adherence (human immunodeficiency virus [HIV] infection, alcoholism, illicit drug use, immigrant or homeless status and/or previous failure to complete). Patients in the DOT programme received medication as out-patients twice a week in pharmacies that supervised adherence and provided socio-sanitary support to patients. RESULTS: There were 101 and 112 patients in the DOT and SAT groups, respectively. Demographic and clinical characteristics were similar in both groups. Differences were observed in risk factors for non-adherence (more immigrants and fewer intravenous drug users in the DOT vs. the SAT groups; P < 0.05). In the DOT group, 76 patients (75.2%) completed treatment and were cured compared to only 30 patients (26.7%) in the SAT group (P < 0.001). Implementation of DOT increased the cost of treatment by 400 Euro per patient compared to SAT. CONCLUSION: In patients at risk for non-adherence, DOT implemented through pharmacy offices was better than SAT; however, completion rates were still low.

In vitro tracheal hyperresponsiveness to muscarinic receptor stimulation by carbachol in a rat model of bleomycin-induced pulmonary fibrosis.

1 Bleomycin-induced lung injury is widely used as an experimental model to investigate the pathophysiology of pulmonary fibrosis but the alterations in the pharmacological responsiveness of airways isolated from bleomycin-exposed animals has been scarcely investigated. The aim of this study was to examine the in vitro tracheal responses to muscarinic receptor stimulation with carbachol in a rat bleomycin model. 2 Concentration-response curves to carbachol (10 nm to 0.1 mm) were obtained in tracheal rings isolated from Sprague-Dawley rats 14 days after endotracheal bleomycin or saline. The intracellular calcium signal in response to carbachol (10 microm) was measured by epifluorescence microscopy using fura-2 in primary cultures of tracheal smooth muscle cells from bleomycin- and saline-exposed rats. Circulating plasma tumour necrosis factor (TNF)-alpha/interleukin (IL)-1beta levels were measured by enzyme-linked immunosorbent assay. 3 Maximal contraction in response to carbachol was significantly greater in tracheal rings from bleomycin-exposed rats compared with controls (15.8 +/- 1.3 mN vs. 11.8 +/- 1.4 mN; n = 19, P < 0.05). 4 Carbachol (10 microm) elicited a transient increase of intracellular calcium with greater increment in tracheal smooth muscle cells from bleomycin-exposed rats compared with controls (372 +/- 42 nmvs. 176 +/- 20 nm; n = 7, P < 0.01). 5 Circulating plasma levels of TNF-alpha/IL-1beta were augmented in bleomycin-exposed rats compared with controls. Tissue incubation with TNF-alpha (100 ng ml(-1))/IL-1beta (10 ng ml(-1)) increased in vitro tracheal responsiveness to carbachol. 6 In conclusion, tracheal contraction in response to muscarinic receptor stimulation with carbachol was increased in bleomycin-exposed rats. This in vitro cholinergic hyperresponsiveness may be related to the augmented levels of inflammatory cytokines in bleomycin-exposed rats.

[Gastrointestinal stromal tumors presenting as pelvic masses]. / Tumores del estroma gastrointestinal que comienzan como masas pelvianas.

Gastrointestinal stromal tumors (GIST) appear in the abdominal cavity in less than 5% of patients. We present two cases of extraintestinal GIST attended in our service and treated with imatinib mesylate. We review the current treatment of these neoplasms with targeted therapies.

[Metallic ureteral stents. Present and future.] / Stents ureterales metálicos. Presente y futuro.

The management of ureteral obstruction of malignant origin or complicated benign obstruction continues to be a challenge for the urological community. In this sense, the use of metallic stents could be considered a useful alternative to the conventional drainage techniques, because it accomplishes the resolution of obstruction in a single procedure, without external diversions and without the adverse effects of current diversions. Another important advantage they offer is that they do not need replacement as frequently as double J catheters or nephrostomy tubes require. From their first applications in the upper urinary tract until now the design of metallic stents has experienced a notable evolution. The main obstacle at the beginning was the use of stents intended for other organic territories, which caused a high rate of failures, since they did not take into consideration in their designs the hostile environment represented by urine for this type of devices, neither the existence of ureteral peristaltism. Thanks to subsequent metallic designs (Memokath, Uventa, Allium Medical URS-stent, Resonance), the current generation of ureteral metallic stents has improved the success rate in comparison to classical designs, accommodating to ureteral dynamics and improving the coating and alloys. Despite these advances, today, their application is limited to very selected patients due to the onset of undesirable effects still associated with theses stents, such as obstructive urothelial hyperplasia, encrustation or migration. The precise knowledge of the physiopathological mechanisms responsible for the cited adverse effects, together with the application of Bioengineering enabling the development of drug eluting metallic stents, biocoated stents, or new biodegradable metallic materials that mitigate or diminish their effects, may be the key to allow the development of the ideal metallic stent.

[Antirreflux ureteral catheters.] / Catéteres ureterales antirreflujo.

Double-J ureteral stents disposal is associated with the appearance of side effects in up to 90% of the patients. The main causes of these symptoms are related to stent's design and the materials they are manufactured from. Vesicoureteral reflux and bladder trigone irritation are the etiopathogenic causes of ureteral stents associated morbidity. Due to this, and in order to improve patients' quality of life, stents that avoid reflux have been developed. Among anti-reflux designs, the first was a double-J stent the bladder tip of which is provided with a polymeric membrane that prevents retrograde flow of urine through its internal drainage channel. This design showed satisfactory vesicaresults, although not statistically significant. Their use in renal transplantation has also been assessed not only to decrease morbidity and ascending infection but also to improve graft survival. Other designs try to thin the distal end and even change it to a surgical suture thread, with the aim of eliminating the internal drainage channel in order to cause the minimum interference with the UVJ. Recently, two prototypes were evaluated in animal models and have achieved reduction of VUR. The first consists of a valve attached to the distal end of a traditional double-J stent, acting as a backflow prevention device. The second design is an intra-ureteral stent that acts like a double-J stent, but without crossing the UVJ and therefore preventing reflux completely. Nowadays, the use of these devices is not implemented in hospitals due to the absence of scientific evidence supporting the superiority of these designs over conventional stents.

[Biodegradable catheters and urinary stents. When?] / Catéteres y stents urinarios biodegradables. ¿Para cuándo?

One of the main wishes in the field of urinary catheters and stents is to arm them with biodegradable characteristics because we consider a failure of these devices the need for retrieval, the forgotten catheter syndrome as well as the adverse effects permanent devices cause after fulfilling their aim. The efforts focused in new designs, coatings and biomaterials aim to increase the biocompatibility of theses internal devices. Lately, there have been correct advances to answer the main challenges regarding biodegradable ureteral devices. Thus, modulation of the rate of degradation has been achieved thanks to new biomaterials and the use of copolymers that enable to choose the time of permanence as it is programmed with conventional double J catheters. Biocompatibility has improved with the use of new polymers that adapt better to the urine. Finally, one of the main problems is elimination of degraded fragments and experimentally it has be demonstrated that new designs elicit controlled degradation, from distal to proximal; using stranding and combination of copolymers degradation may be caused by dilution, reducing fragmentation to the last stages of life of the prosthesis. Moreover, it has been demonstrated that biodegradable catheters potentially may cause less urinary tract infection, less encrustation and predictably they will diminish catheter morbidity, since their degradation process reduces adverse effects. Regarding the development of biodegradable urethral stents, it is necessary to find biomaterials that enable maintaining their biomechanical properties in the long term, keeping open the urethral lumen both in patients with BPH and urethral stenosis. Modulation of the time of degradation of the prosthesis has been achieved, but the appearance of urothelial hyperplasia is still a constant in the initial phases after implantation. The development of drug eluting stents, anti-proliferative or anti-inflammatory, as well as biodegradable stents biocoated is a field from which it is expected the arrival of the solution of theses adverse effects. Therefore, many features need to be improved to obtain biodegradable stents, but over the last years some turning points have been accomplished thanks to the advances in Bioengineering, allowing to foresee safe and effective solutions in the nearest future.

Contraction of human airways by oxidative stress protection by N-acetylcysteine.

We examined the in vitro effects of tert-butylhydroperoxide (tBu-OOH) in human bronchial muscle. tert-Butylhydroperoxide produced concentration-dependent contractions of bronchial rings (maximum effect was 56.5 +/- 9.6% of contraction by 1 mM acetylcholine; effective concentration 50% was approximately 100 microM). tert-Butylhydroperoxide (0.5 mM)-induced contraction was enhanced by epithelial removal but abolished by indomethacin (cyclooxygenase inhibitor) and zileuton (lipoxygenase inhibitor). tert-Butylhydroperoxide produced a transient rise in intracellular calcium in human cultured airway smooth muscle cells (HCASMC). The bronchial reactivity to acetylcholine and histamine was not altered by tBu-OOH. In HCASMC, tBu-OOH (0.5 mM, 30 min) increased malondialdehyde levels (MDA; from 7.80 +/- 0.83 to 26.82 +/- 1.49 nmol mg(-1) protein), accompanied by a decrease of reduced glutathione (GSH; from 16.7 +/- 2.6 to 6.9 +/- 1.9 nmol mg(-1) protein) and an increase of oxidized glutathione (from 0.09 +/- 0.03 to 0.18 +/- 0.03 nmol mg(-1) protein). N-acetylcysteine (0.3 mM) inhibited by approximately 60% the bronchial contraction resulting from tBu-OOH (0.5 mM) and protected cultured cells exposed to tBu-OOH (MDA was lowered to 19.51 +/- 1.19 nmol mg(-1) protein, and GSH content was replenished). In summary, tBu-OOH caused contraction of human bronchial muscle mediated by release of cyclo-oxygenase and lipoxygenase products without producing airways hyperreactivity. N-acetylcysteine decreases tBu-OOH-induced contraction and protects human cultured airway smooth muscle cells exposed to tBu-OOH.

Antagonism of calcium by zinc in guinea-pig isolated taenia caeci and trachealis muscle.

1 In guinea-pig isolated taenia caeci and trachealis bathed in a K+-rich, Ca2+-free medium, CaCl2 (0.01-10 mM) produced a concentration-dependent contraction. Zn2+ (0.01-1 mM), Cd2+ (0.01-1 mM), verapamil (0.01-100 microM) and trifluoperazine (1-100 microM) were effective antagonists of CaCl2-induced responses. 2 Zn2+ and Cd2+ in concentrations from 0.01 to 1 mM were without effect on the tone of taenia and trachea in normal Tris solution. Conversely, Zn2+ and Cd2+, in concentrations of 1 mM, caused contraction of these tissues in a K+-rich, Ca2+-free medium. Zn2+ (1 mM)-induced contractions of taenia and trachea were completely inhibited by verapamil (10 microM). 3 In taenia and trachea skinned of their plasma membranes, tension development induced by Ca2+ (10 microM or 1 microM, respectively) was unaffected by verapamil (100 microM), whereas trifluoperazine (100 microM) depressed the maximal tension produced by Ca2+. Segments of skinned preparations contracted in response to low concentrations of Zn2+ (10 microM) or Cd2+ (10 microM). 4 It is concluded that Zn2+ may suppress Ca2+-induced spasm by a direct action on the binding sites of the Ca2+ channel.

Pharmacological analysis of the responsiveness of guinea-pig lung parenchymal strip to dopamine.

Responses to dopamine were examined in the guinea-pig isolated lung parenchymal strip. Complete cumulative concentration-response curves to dopamine exhibited a biphasic pattern with a small initial contraction at concentrations below 10(-5) M followed by a dose-dependent relaxation at higher concentrations. Phentolamine (10(-5) M) completely abolished the contractile component and enhanced sensitivity and maximal relaxation to dopamine. In the presence of phentolamine, propranolol antagonized the dopamine-induced relaxation (pA2 = 8.54 +/- 0.07). In the presence of propranolol (10(-6) M), dopamine produced a dose-related contraction displaced to the right by phentolamine. Incubation with haloperidol (10(-5) M) did not modify the characteristics of the concentration-response curve to dopamine. Pretreatment with reserpine abolished the contraction to dopamine without affecting its relaxant response. Cocaine significantly increased the pD2 value of dopamine in the presence of propranolol. It is concluded that dopamine produced both relaxation of lung parenchymal strip due to direct activation of beta-adrenoceptors and contraction mediated through direct and indirect (catecholamine release) actions at alpha-adrenoceptors. There is no evidence in favour of the existence of specific dopamine-receptors in this preparation.

Effects of beta-adrenoceptor drug stimulation on various models of gastric ulcer in rats.

1. Experiments were designed to evaluate the effect of the pharmacological activation of beta-adrenoceptors on various models of gastric ulcer in the rat. 2. Pretreatment with the beta-adrenoceptor stimulant drugs, isoprenaline or salbutamol, significantly inhibited stress-induced gastric ulcers. This anti-ulcer effect was abolished by propranolol but not by atenolol, suggesting that beta 2-adrenoceptors mediate this response. 3. In the pylorus-ligation model, salbutamol inhibited lesion formation and reduced the intragastric content of hydrogen ions, histamine and pepsin although the latter was only affected with the higher dose of salbutamol. 4. Salbutamol also prevented the ulcerogenic action on the gastric mucosa of an exogenously perfused artificial gastric juice, showing that the anti-ulcer effect is not necessarily dependent on acid inhibition. 5. Salbutamol also reduced the formation of acute ulcers induced by various iatrogenic means (histamine, polymyxin B, reserpine and indomethacin). 6. Long-term treatment with salbutamol accelerated the healing of experimental chronic gastric ulcer. 7. In anaesthetized rats, salbutamol produced a dose-related increase in mucosal blood flow which may contribute to its mode of action. 8. It is concluded that beta-adrenoceptor agonists exert preventive and curative effects on gastric damage induced in the rat. This effect seems specific and mediated through beta-adrenoceptor activation.