Randomized clinical trial of chewing gum after laparoscopic colorectal resection.

BACKGROUND: Chewing gum may enhance intestinal motility after surgery. This trial studied whether chewing gum could lead to a further reduction in ileus in patients who had a laparoscopic colorectal resection and followed an enhanced recovery programme. METHODS: Patients undergoing laparoscopic colorectal resection were randomized to a control or intervention group. Patients in the control group received a standardized recovery programme. Patients in the intervention group were, in addition, given chewing gum three times daily from day 1 until discharge. Primary outcome measures were time to first flatus and first bowel motion. Time to feeling hungry and hospital stay were secondary outcome measures. RESULTS: Forty-one patients were randomized into each group. Thirty-seven patients underwent rectal resection and 45 had a colonic resection. Time to passage of flatus was shorter (18 versus 34 h; P = 0·007), first bowel motion occurred earlier (19 versus 44 h; P = 0·001) and time to feeling hungry was earlier (16 versus 25 h; P = 0·001) in the intervention group. There was no difference in the duration of hospital stay (5 days in the intervention group versus 5·5 days in the control group). Subgroup analyses revealed that the benefits of chewing gum were clearer in patients who had a colonic resection, with a shorter time to first flatus (20 versus 35 h; P = 0·043), first bowel motion (19 versus 53 h; P = 0·014) and feeling hungry (14 versus 40 h; P = 0·001). No adverse events were attributed to chewing gum. CONCLUSION: Chewing gum is a simple intervention that speeds intestinal transit in patients managed with a recovery programme after laparoscopic colorectal resection. REGISTRATION NUMBER: NCT02419586 (https://clinicaltrials.gov/).

Meta-analysis of the cardiovascular benefits of intensive lipid lowering with statins.

OBJECTIVE: To evaluate the efficacy of intensive lipid lowering with higher-dose statins. METHODS: Meta-analysis of seven randomized controlled trials comprising 50,972 participants. RESULTS: Mean follow-up was 3.1 years with mean age 63 years. Final LDL-C levels in intensive lipid-lowering group were 1.42-2.07 mmol/l compared to 2.1-3.5 mmol/l in the less intensive or control group. The intensive arm had significantly lower risks for stroke OR 0.80 (95% CI 0.71-0.89); major coronary events OR 0.74 (95% CI 0.65-0.83); cardiovascular disease (CVD) or coronary heart disease (CHD) deaths OR 0.84 (95% CI 0.74-0.95). Significantly higher liver enzyme abnormalities occurred in intensive group* (OR 3.96; 95% CI 2.08-7.53), but it was not associated with drug discontinuations (OR 1.20; 95% CI 0.88-1.64). CONCLUSION: In those at high risk of cardiovascular events, intensive lipid lowering with statins to LDL-C level <2.1 mmol/l significantly reduces risk of stroke, major coronary events and CVD or CHD deaths compared to LDL-C level ≥ 2.1 mmol/l. [*Correction added on 11 January 2011 after first online publication on 27 October 2010. The phrase, "Significantly higher liver enzyme abnormalities occurred in less intensive group", was amended to "Significantly higher liver enzyme abnormalities occurred in intensive group".].

Perceptions and attitudes of rehabilitation medicine physicians on complementary and alternative medicine in Australia.

BACKGROUND: The growing demand for complementary and alternative medicine (CAM) is undeniable. We report a first study about the attitudes and behaviour of Australian rehabilitation physicians to CAM. METHODS: A prospective cross-sectional survey was undertaken to document the prevalence of, knowledge about and referrals to CAM therapies and their perceived effectiveness, by a sample of Australian rehabilitation physicians. RESULTS: Thirty-six out of 94 actively practising rehabilitation physicians from the Australasian Faculty of Rehabilitation Medicine, the Royal Australasian College of Physicians, replied to the survey, a response rate of 38%, and 85% reported familiarity with CAM, the most familiar therapies being acupuncture (80%), yoga (74%) and Tai-Chi (72%). CAM referral was reported in 84%, 38% personally used CAM, 94% of patients enquired about CAM therapies, 32% of respondents routinely enquired about CAM use. Age, sex and year of Fellowship were not associated with familiarity, personal use or frequency of patient enquiry about CAM. Those who reported to be very familiar with CAM were more likely to routinely enquire about CAM use (P = 0.028) and be more confident in prescribing certain CAM therapies (P < 0.05). CONCLUSION: Australian rehabilitation physicians report similar CAM referral rates to Canadian physiatrists and Australian general practitioners. The most commonly prescribed therapies were acupuncture, yoga and Tai-Chi. Almost all patients use CAM therapies, but only a minority of rehabilitation physicians enquires about CAM use on a regular basis. The latter may avoid potentially harmful drug interactions, as well as improve the quality of the physician-patient relationship.

Pathogenesis of COPD. Part II. Oxidative-antioxidative imbalance.

Chronic obstructive pulmonary disease (COPD) represents a serious global health problem that affects the aged. This State of the Art article summarises previous studies on oxidative-antioxidative imbalance in patients with stable COPD or in acute exacerbations. Recent literature in this field reports conflicting findings. Several studies on markers of oxidative stress have demonstrated increased production of oxidants in exhaled air, breath condensates or induced sputum. The primary defence against oxidants is endogenous antioxidants, which are altered in COPD. Some studies have demonstrated a marked decrease in plasma antioxidant capacity, while other studies have shown opposite findings. A few studies have shown higher erythrocyte superoxide dismutase (SOD) activity in COPD patients and healthy smokers than those in healthy non-smokers. In contrast, we found no differences in erythrocyte SOD activity and elevated erythrocyte catalase activity in Chinese patients with COPD compared with healthy smokers matched for age and pack-years smoked. Possible reasons for such discrepancies could be related to differences in inter-individual variations in antioxidant capacity as a result of different populations and also differences in methodologies between studies.

Protective effects of a glucocorticoid on downregulation of pulmonary beta 2-adrenergic receptors in vivo.

We investigated the in vivo effects of a glucocorticoid on beta-agonist-induced downregulation of beta 1- and beta 2-adrenergic receptors (determined by [125I]iodocyanopindolol binding), mRNA expression (assessed by Northern blotting), and gene transcription (using nuclear run-on assays) in rat lung. Dexamethasone (Dex) (0.2 mg/kg/d, days 1-8) increased beta 1- and beta 2-receptor numbers by 70 and 69% above control, respectively, but did not change their mRNA expression. Isoproterenol (Iso) (0.96 mg/kg/d, days 2-8) decreased beta 1- and beta 2-receptor numbers by 48 and 51%, respectively, and also reduced mRNA expression by 69 and 57%, respectively. The combination of Dex and Iso resulted in no net change in beta 2-receptor number and its mRNA expression, although there was a significant reduction in beta 1-receptor number and mRNA expression. The mapping of beta 1- and beta 2-receptors by receptor autoradiography confirmed these findings over alveoli, epithelium, endothelium, and airway and vascular smooth muscle. We also measured the activation of the transcription factor, cyclic AMP response element binding protein (CREB) using an electrophoretic mobility shift assay. CREB-like DNA-binding activity was decreased after Iso treatment but this decrease was prevented after treatment with Dex. Nuclear run-on assays revealed that the transcription rate of the beta 1-receptor gene did not alter after Dex treatment, but was reduced after Iso treatment. The transcription rate of the beta 2-receptor gene was increased after Dex treatment by approximately twofold, but there was no change after Iso treatment. We conclude that glucocorticoids can prevent homologous downregulation of beta 2-receptor number and mRNA expression at the transcriptional level without affecting beta 1-receptors and that the transcription factor CREB may be involved in this phenomenon. Such an effect may have clinical implications for preventing the development of tolerance to beta 2-agonists in asthmatic patients treated with beta-agonist bronchodilators.

Mechanisms of impaired beta-adrenoceptor-induced airway relaxation by interleukin-1beta in vivo in the rat.

We studied the in vivo mechanism of beta-adrenergic receptor (beta-AR) hyporesponsiveness induced by intratracheal instillation of interleukin-1beta (IL-1beta, 500 U) in Brown-Norway rats. Tracheal and bronchial smooth muscle responses were measured under isometric conditions ex vivo. Contractile responses to electrical field stimulation and to carbachol were not altered, but maximal relaxation induced by isoproterenol (10(-6)-10(-5) M) was significantly reduced 24 h after IL-1beta treatment in tracheal tissues and to a lesser extent, in the main bronchi. Radioligand binding using [125I]iodocyanopindolol revealed a 32+/-7% reduction in beta-ARs in lung tissues from IL-1beta-treated rats, without any significant changes in beta2-AR mRNA level measured by Northern blot analysis. Autoradiographic studies also showed significant reduction in beta2-AR in the airways. Isoproterenol-stimulated cyclic AMP accumulation was reduced by IL-1beta at 24 h in trachea and lung tissues. Pertussis toxin reversed this hyporesponsiveness to isoproterenol but not to forskolin in lung tissues. Western blot analysis revealed an IL-1beta-induced increase in Gi(alpha) protein expression. Thus, IL-1beta induces an attenuation of beta-AR-induced airway relaxation through mechanisms involving a reduction in beta-ARs, an increase in Gi(alpha) subunit, and a defect in adenylyl cyclase activity.

Albuterol-induced downregulation of Gsalpha accounts for pulmonary beta(2)-adrenoceptor desensitization in vivo.

The aim of the present study was to develop a chronic in vivo model of pulmonary beta(2)-adrenoceptor desensitization and to elucidate the nature and molecular basis of this state. Subcutaneous infusion of rats with albuterol for 7 days compromised the ability of albuterol, given acutely, to protect against acetylcholine-induced bronchoconstriction. The bronchoprotective effect of prostaglandin E(2), but not forskolin, was also impaired, indicating that the desensitization was heterologous and that the primary defect in signaling was upstream of adenylyl cyclase. beta(2)-Adrenoceptor density was reduced in lung membranes harvested from albuterol-treated animals, and this was associated with impaired albuterol-induced cyclic adenosine monophosphate (cAMP) accumulation and activation of cAMP-dependent protein kinase ex vivo. Gsalpha expression was reduced in the lung and tracheae of albuterol-treated rats, and cholera toxin-induced cAMP accumulation was blunted. Chronic treatment of rats with albuterol also increased cAMP phosphodiesterase activity and G protein-coupled receptor kinase-2, but the extent to which these events contributed to beta(2)-adrenoceptor desensitization was unclear given that forskolin was active in both groups of animals and that desensitization was heterologous. Collectively, these results indicate that albuterol effects heterologous desensitization of pulmonary Gs-coupled receptors in this model, with downregulation of Gsalpha representing a primary molecular etiology.

Polymorphisms of glutathione S-transferase genes and functional activity in smokers with or without COPD.

OBJECTIVE: To determine the role of polymorphisms of genes regulating glutathione S-transferase (GST) and its plasma GST activity in the pathogenesis of chronic obstructive pulmonary disease (COPD). DESIGN: Case-control study. METHODS: One hundred and sixty-three patients with stable COPD from several community or regional hospitals were matched for age and pack-years smoked with the same number of health controls from the general population. Each participant underwent an interview-based respiratory and smoking questionnaire, lung function testing and gave a blood sample. Genotyping was carried out using a polymerase chain reaction-based method for polymorphisms of glutathione S-transferase theta 1 (GSTT1), glutathione S-transferase mu 1 (GSTM1) and glutathione S-transferase P 1 (GSTP1) genes. Plasma GST activity was measured using the spectrofluorometric method. RESULTS: There were no significant differences in the distribution of various genotypes of polymorphisms of GSTT1, GSTM1 and GSTP1 between COPD patients and healthy controls. GST activity was significantly higher in patients compared with controls, irrespective of their different genotypes, and was not different between patients with different levels of airflow obstruction. CONCLUSION: Polymorphisms of GSTT1, GSTM1 and GSTP1 genes are unlikely to be involved in the pathogenesis of COPD in Chinese in Hong Kong and Southern China.

Long-term carbachol treatment-induced down-regulation of muscarinic M2-receptors but not m2 receptor mRNA in a human lung cell line.

1. The molecular mechanisms involved in the regulation of muscarinic receptor gene expression are poorly understood. We have investigated the effect of homologous stimulation on the regulation of M2 muscarinic receptor protein and gene in human embryonic lung fibroblasts (HEL 299 cells). 2. Saturation studies performed with the non-selective hydrophilic ([3H]-N-methyl-scopolamine, [3H]-NMS) and lipophilic (3H]-quinuclidinyl benzilate, [3H]-QNB) muscarinic antagonists revealed a single class of high affinity binding sites. 3. Carbachol (1 mM) induced a rapid down-regulation of [3H]-NMS binding sites. Within 12 h, the process had approached steady state with 40 to 60% loss of receptors at 12 and 24 h. 4. The loss of [3h]-QNB binding sites (40% reduction at 24 h) occurred at a slower rate than did loss of [3H]-NMS binding sites as a result of receptor sequestration. 5. Carbachol treatment was accompanied by a functional desensitization of the receptor after 24 h of agonist treatment. In untreated cells, forskolin induced a large increase in cyclic AMP accumulation which was inhibited significantly by carbachol. The inhibitory effect of carbachol on forskolin-induced cyclic AMP accumulation was lost following 24 h carbachol stimulation. 6. The steady state level of muscarinic m2 mRNA measured by Northern blot analysis was not affected by carbachol had no effect on the stability of m2 mRNA. 7. The rate of transcription of m2 muscarinic receptor gene as measured by nuclear RNA run-on assay was unaltered by carbachol stimulation. 8. These results suggest that homologous sequestration, desensitization, and down-regulation of M2 modifications of m2 muscarinic receptor mRNAs.

Desensitization of the histamine H1-receptor and transcriptional down-regulation of histamine H1-receptor gene expression in bovine tracheal smooth muscle.

We have investigated the role of protein kinase C (PKC) in the desensitization of histamine H1-receptors and in the expression of the histamine H1-receptor gene in airway smooth muscle. Prolonged 4beta-phorbol 12,13 dibutyrate (PDBu) pretreatment (4 h, 100 nM-1 microM) of bovine trachealis caused a concentration-dependent loss of contraction in response to histamine H1-receptor stimulation, which was associated with a concentration-dependent decrease in histamine-induced total [3H]-inositol phosphates accumulation. In contrast, the responses to sodium fluoride, a direct G-protein activator, were unalterd by PDBu (100-300 nM) pre-incubation and only slightly reduced following incubation with 1 microM PDBu. A selective PKC inhibitor, GF 109203X, partially blocked the PDBu (1 microM)-induced desensitization and completely blocked the effect of 100 nM PDBu, confirming the involvement of PKC. Binding experiments using [3H]-pyrilamine revealed a class of high-affinity binding sites within the range for the histamine H1 receptor in airway smooth muscle. PDBu (1 microM) pretreatment for 4 h did not change the number of histamine H1 receptors. PDBu (1 microM) exposure caused a time-dependent reduction in the steady-state levels of histamine H1-receptor mRNA, which was inhibited by pre-incubation with GF 109203X and by cycloheximide, a protein synthesis inhibitor. Nuclear run-on assays revealed a 50% reduction in the rate of histamine H1-receptor gene transcription after 17 h PDBu pretreatment, whereas mRNA stability was not affected by PDBu pretreatment (17 h). In conclusion, we have shown a PKC-mediated desensitization of the histamine H1-receptor in BTSM and a transcriptional down-regulation of the histamine H1-receptor gene expression, which requires new protein synthesis.

Regulation of H1-receptor coupling and H1-receptor mRNA by histamine in bovine tracheal smooth muscle.

1. Pretreatment of bovine tracheal smooth muscle (BTSM) with histamine (1-100 microM, 1 h) induced a concentration-dependent desensitization of the contractile response to subsequently administered histamine, with a reduction of the maximum response of 72 +/- 8% (n = 5) following pre-exposure to 100 microM histamine. In contrast, concentration-response curves to the muscarinic agonist, methacholine were not affected following histamine pretreatment, indicating a homologous desensitization. Furthermore, concentration-response curves to NaF, a G-protein activator, were not altered following histamine pre-incubation. 2. The histamine H1-receptor (H1R) desensitization could be antagonized by mepyramine (an H1-receptor antagonist, 1 microM) but not by cimetidine (an H2-receptor antagonist, 10 microM), indicating that the desensitization occurred via stimulation of histamine H1-receptors, without evidence for the involvement of histamine H2-receptors. 3. Indomethacin (10 microM) did not block the H1R desensitization, suggesting no involvement of prostaglandins. Furthermore, histamine pre-incubation in calcium free medium still induced a functional uncoupling of H1R. 4. GF 109203X, a protein kinase C (PKC) inhibitor, and H-7, a non-selective kinase inhibitor, did not antagonize the homologous H1R desensitization. 5. The steady-state level of H1R mRNA, assessed by Northern blot analysis, was not affected by prolonged histamine exposure (100 microM, 0.5, 1, 2, 4, 16 and 24 h). 6. These results suggest that histamine induces desensitization of the H1R at the level of the receptor protein, which involves a mechanism independent of PKC, PKA, PKG and calcium influx, suggesting the involvement of a receptor-specific kinase.

Chronic systemic administration of salmeterol to rats promotes pulmonary beta(2)-adrenoceptor desensitization and down-regulation of G(s alpha).

1. The aim of the present study was to examine the effects of chronic infusion of the long-acting agonist salmeterol on pulmonary beta(2)-adrenoceptor function in Sprague-Dawley rats in vivo and to elucidate the molecular basis of any altered state. 2. Systemic administration of rats with salmeterol for 7 days compromised the ability of salmeterol and prostaglandin E(2) (PGE(2)), given acutely by the intravenous route, to protect against ACh-induced bronchoconstriction when compared to rats treated identically with vehicle. 3. beta(1)- and beta(2)-adrenoceptor density was significantly reduced in lung membranes harvested from salmeterol-treated animals, which was associated with impaired salmeterol- and PGE(2)-induced cyclic AMP accumulation ex vivo. 4. Three variants of G(s alpha) that migrated as 42, 44 and 52 kDa peptides on SDS polyacrylamide gels were detected in lung membranes prepared from both groups of rats but the intensity of each isoform was markedly reduced in rats that received salmeterol. 5. The activity of cytosolic, but not membrane-associated, G-protein receptor-coupled kinase was elevated in the lung of salmeterol-treated rats when compared to vehicle-treated animals. 6. The ability of salmeterol, administered systemically, to protect the airways of untreated rats against ACh-induced bronchoconstriction was short-acting (t(off) approximately 45 min), which contrasts with its long-acting nature when given to asthmatic subjects by inhalation. 7. These results indicate that chronic treatment of rats with salmeterol results in heterologous desensitization of pulmonary G(s)-coupled receptors. In light of previous data obtained in rats treated chronically with salbutamol, we propose that a primary mechanism responsible for this effect is a reduction in membrane-associated G(s alpha). The short-acting nature of salmeterol, when administered systemically, and the reduction in beta-adrenoceptor number may be due to metabolism to a biologically-active, short-acting and non-selective beta-adrenoceptor agonist.

Calcitonin gene-related peptide vasodilation of human pulmonary vessels.

Human calcitonin gene-related peptide (CGRP) is localized to sensory neurons in pulmonary vessels and is a potent vasodilator. We have characterized the effects of CGRP in human pulmonary vessels and localized the receptors for this peptide by autoradiography. Fresh human lung tissue was obtained from eight patients undergoing surgery and small (200-400 microns ID) pulmonary arteries and veins were dissected free of surrounding connective and pulmonary tissue. Pairs of vessels were studied and in one of each pair the endothelium was left intact and from the other of each pair the endothelium was removed by gentle abrasion. For functional studies arteries (n = 9) and veins (n = 9) were suspended in an organ bath, precontracted with 1 microM prostaglandin F2 alpha. CGRP (10 pM to 10 microM) was added in a cumulative manner. CGRP caused a dose-dependent relaxation of endothelium intact human pulmonary arteries and veins with log EC50 values of -8.01 +/- 0.35 and -8.70 +/- 0.40, respectively (not significant). Removal of the endothelium did not diminish the vasodilator potency of CGRP in either vessel. For autoradiographic studies, cryostat sections of the small human pulmonary vessels with or without endothelium were used. 125I-CGRP densely labeled CGRP receptors on vascular smooth muscle and endothelial removal did not have any effect on grain density. We concluded that CGRP is a potent vasodilator of human pulmonary arteries and veins that is not dependent on an intact endothelium. These functional studies correlate with the distribution of CGRP receptors as localized by autoradiography.

Autoradiographic localization of calcitonin gene-related peptide (CGRP) binding sites in human and guinea pig lung.

125I-Human calcitonin gene-related peptide (hCGRP) binding sites were localized in human and guinea pig lungs by an autoradiographic method. Scatchard analysis of saturation experiments from slide-mounted sections of guinea pig lung displayed specific 125I-hCGRP binding sites with a dissociation constant (Kd) of 0.72 +/- 0.05 nM (mean +/- S.E.M., n = 3) and a maximal number of binding sites (Bmax) of 133.4 +/- 5.6 fmol/mg protein. In both human and guinea pig lung, autoradiography revealed that CGRP binding sites were widely distributed, with particularly dense labeling over bronchial and pulmonary blood vessels of all sizes and alveolar walls. Airway smooth muscle and epithelium of large airways was sparsely labeled but no labeling was found over submucosal glands. This localization corresponds well to the reported pattern of CGRP-like immunoreactive innervation. The findings of localization of CGRP binding sites on bronchial and pulmonary blood vessels indicate that CGRP may be important in the regulation of airway and pulmonary blood flow.

Characterization and autoradiographic mapping of [3H]CP96,345, a nonpeptide selective NK1 receptor antagonist in guinea pig lung.

We have studied binding and distribution of NK1 receptors in guinea pig lung using [3H]CP96,345. Kinetic studies showed that specific binding of [3H]CP96,345 was rapid and reversible, giving a kinetic dissociation constant (Kd) of 0.28 +/- 0.05 nM. The specific binding was also saturable and Scatchard analysis indicated a single class of binding site with an equilibrium Kd of 0.12 +/- 0.03 nM and maximum binding capacity (Bmax) of 107.0 +/- 10.3 fmol/mg of protein. Competition studies showed the rank order of affinity for agonists and antagonists as follows: SP > NKA = septide >> NKB = senktide; CP96,345 > FK888 > FK224 > L668169. NK3 agonists, NK2-selective antagonists, and a calcium channel blocker, diltiazem, showed no displacement, indicating high selectivity for NK1 receptors. Autoradiographic mapping showed specific labeling over airway smooth muscle from central to peripheral airways, submucosal glands, and nerve fibers of trachea. The labeling of airway epithelium was increased with diminishing size of airways. Pulmonary blood vessels were also moderately labeled and there was sparse labeling over alveolar walls. [3H]CP96,345 may provide a useful tool to evaluate NK1 receptor expression in peripheral organs.

Autoradiographic mapping of pulmonary NK1 and NK2 tachykinin receptors and changes after repeated antigen challenge in guinea pigs.

An autoradiographic technique was used to study the distribution of changes in pulmonary NK1 and NK2 receptors in guinea pig lung after repeated antigen challenge. Specific labeling of [3H]CP96345 (NK1 receptors) and [3H]SR48968 (NK2 receptors) was localized over the tracheal and bronchial smooth muscle; the density of binding increased towards smaller airways with a higher density for [3H]CP96345 binding. Bronchial epithelium and pulmonary blood vessels were also labeled densely with [3H]CP96345. No remarkable difference in the pattern of distribution of pulmonary NK1 and NK2 tachykinin receptors was observed between control, vehicle-challenged, and repeatedly antigen-challenged (weekly for three times) guinea pigs. A significant reduction in specific labeling of [3H]CP96345 (p < 0.01) and [3H]SR48968 (p < 0.05) over pulmonary structures was observed in antigen-challenged compared to control or vehicle-challenged animals. This study provides evidence that NK1 and NK2 tachykinin receptors are both localized to smooth muscle of all sizes in guinea pig airways and provides further evidence for a discrete distribution of NK1 and NK2 tachykinin receptors, consistent with their relative functional activities. In an established model of airway inflammation a decrease in the expression of NK1 and NK2 tachykinin receptors was evident on several different cell types within the lung, and this could influence airway and vascular reactivity.

Tachykinin control of ferret airways: mucus secretion, bronchoconstriction and receptor mapping.

The effects of synthetic tachykinin receptor agonists on mucus secretion by ferret trachea was determined in vitro in Ussing chambers using 35SO4 as a mucus marker and the synthetic peptides [Sar9,Met(O2)11]substance P (SarSP), [beta Ala8]neurokinin A-(4-10) and [MePhe7] neurokinin B which are selective for NK1, NK2 and NK3 tachykinin-receptors respectively. The bronchomotor effects of the same agonists were also studied in vitro and tachykinin receptors were localized by autoradiographic mapping. SarSP was the only synthetic agonist able to elicit a concentration-dependent increase in mucus secretion and was much more potent than SP. The EC50 for SarSP was 1.7 x 10(-6) M. Moreover, the maximal increase in release of 35SO4 produced by SarSP 10(-5) M was 95% of the increase produced by methacholine 10(-4) M indicating that this concentration of SarSP induced a near maximal secretory response. There was no significant difference in the secretory action of SP administered from the luminal or the submucosal side of the tissue. Only the NK2 agonist was able to produce a concentration-dependent contractility of bronchial ring preparations and its effect was relatively weak (EC50 6.4 x 10(-6) M). Capsaicin (10(-5) M) produced only a slight increase in tracheal mucus secretion (28 +/- 5%; n = 6) and was completely ineffective in inducing bronchoconstriction. Binding sites for [125I]-Bolton Hunter SP were more evident than sites for [125I]-NKA on submucosal glands and epithelium. In contrast, only binding sites to NKA could be observed over the smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoradiographic visualization of bradykinin receptors in human and guinea pig lung.

High affinity [3H]bradykinin (BK) receptor binding sites have been identified in human and guinea pig lung sections by in vitro autoradiography. [3H]BK was incubated with tissue sections for 120 min at 25 degrees C and non-specific binding determined by incubating adjacent serial sections in the presence of unlabelled BK. In saturation experiments with guinea pig lung sections, a single class of high affinity binding sites was identified with an apparent dissociation constant (Kd) of 0.5 +/- 0.1 nM and a maximal binding capacity (Bmax) of 35.2 +/- 2.9 fmol/mg protein (n = 5). The binding of [3H]BK was inhibited by unlabelled BK and NPC 349 (a specific B2 antagonist) at IC50 of 2.7 +/- 0.4 and 87 +/- 9 nM (n = 3), respectively. In contrast, no inhibition was found at 1 microM for a variety of vasoactive peptides such substance P, calcitonin gene-related peptide, vasoactive intestinal peptide and des-Arg9-[Leu8]BK (a specific B1-antagonist). Autoradiography revealed that BK receptors were widely distributed in human and guinea pig lung, with dense labelling over bronchial and pulmonary blood vessels of all sizes and in the lamina propria immediately subjacent to the basal epithelial cell layer in large airways. Airway smooth muscle was sparsely labelled in large airways, but greater labelling in smaller airways. There was also detectable labelling over submucosal glands and nerve fibres in human intrapulmonary bronchi and over alveolar walls in both species. The high density of BK receptors on bronchial and pulmonary blood vessels indicate that BK may play an important role in the regulation of airway and pulmonary blood flow, as well as airway epithelial regulation.