A retrospective comparison of infliximab versus adalimumab as induction and maintenance therapy for Crohn disease.

BACKGROUND: In Australia, infliximab (IFX) and adalimumab (ADA) are available for the treatment of moderate-severe Crohn disease (CD) refractory to conventional therapies, with minimal local data comparing their efficacy. AIM: The aim of this study was to compare clinical and biochemical outcomes at 3 and 12 months between patients receiving induction and maintenance therapy with IFX versus ADA. METHODS: Retrospective single-centre audit of all patients commenced on IFX or ADA as their first anti-tumour necrosis factor agent between July 2007 and May 2012. Clinical and biochemical parameters were compared pre-commencement, 3 and 12 months post-commencement. RESULTS: A total of 81 patients was included in the study; 63 IFX-treated and 18 ADA-treated. Significant Crohn disease activity index (CDAI) reductions were noted within both groups at 3 months (P < 0.001) and 12 months (P < 0.001). Similarly, significant reductions were noted in steroid doses within groups at 3 months (P < 0.05) and 12 months (P < 0.05), with notable reductions in C-reactive protein (CRP) at 3 months within groups (P < 0.05). Adverse events occurred in 14.3% of IFX and 11.1% of ADA patients. Comparing IFX with ADA, no difference was shown between groups in CDAI reductions at 3 months (P = 0.94) and 12 months (P = 0.95), steroid dosing at 3 months (P = 0.23) and 12 months (P = 0.81), and CRP reduction at 3 months (P = 0.33) and 12 months (P = 0.62). Fistula-related admissions were significantly reduced in IFX patients (100% reduction post-IFX vs 66.7% post-ADA) (P = 0.01). CONCLUSION: Clinical and biochemical outcomes were similar in patients treated with IFX or ADA as induction and maintenance therapy for CD. However, significant reductions were noted in admissions relating to fistulising disease in IFX patients.

Faecal calprotectin: current usage and perceived beneficial effects of third-party funding on rates of colonoscopy by Australian gastroenterologists.

BACKGROUND: Studies have suggested a diagnostic role for faecal calprotectin (FC) in patients with gastroenterological disorders. AIM: To investigate Australian gastroenterologists' (GE) views on FC use and to elicit factors that affect physicians' choices. METHODS: Electronic surveys were sent out to 405 consultants and 34 registrars in Australia. Respondents who answered <50% of the survey were excluded. RESULTS: In all, 140 participants provided a >50% response; 73% reported using FC in their clinical practice. Factors cited by non-users in restricting their FC use included cost (24%), availability (47%) and familiarity (18%). Even among users, 69% cited funding as a major deciding factor; 98 and 86% of FC users believed that the test is a reliable method of differentiating between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) and assessing for mucosal healing in IBD respectively. Of non-users, 78 and 58%, respectively, would use FC to differentiate IBD from IBS and assess for mucosal healing in IBD, if FC testing was Medical Benefits Schedule (MBS) listed. Both users (79%) and non-users (68%) reported that use of FC to defer or avoid colonoscopies was likely if the test was MBS funded. CONCLUSION: Australian GE endorse the use of FC to discriminate between IBD and IBS, to check for mucosal healing in IBD and to reduce colonoscopy rates. Absence of MBS funding is an important factor contributing to the lack of usage of FC, in addition to the lack of familiarity with FC testing and availability.

Dose tailoring of anti-tumour necrosis factor-alpha therapy delivers useful clinical efficacy in Crohn disease patients experiencing loss of response.

BACKGROUND: 'Dose tailoring' of anti-tumour necrosis factor alpha (TNF-α) therapy in Crohn disease (CD), by dose escalation, or shortening of dosing intervals, has been suggested to regain clinical response following a flare in a proportion of patients. However, reported outcome data are sparse and none exists from Australia. METHOD: In an observational multicentre, retrospective study, the impact of anti-TNF-α dose tailoring on corticosteroid use, the need for surgery and physician perception of clinical efficacy was examined in a real-world setting at six Australian adult teaching hospitals. Demographics, disease characteristics, medications, indication for and duration of dose tailoring were documented. RESULTS: Fifty-five CD patients were identified as requiring dose tailoring and secondary loss of response was the indication in 96%. Either adalimumab (64%) or infliximab (36%) was dose escalated for a median of 5 months (range 1-47), with a median of 20 months follow up (range 3-65). At 3 months, dose tailoring reduced the mean number of days on high-dose corticosteroids (45 vs 23, P = 0.01). Most (78%) patients remained resection free, and 73% of physicians reported good clinical efficacy of dose tailoring. Of those who de-escalated therapy due to induction of remission, long-term (>12 months) follow up and complete data on steroid use were available in 15/28, with 12/15 (80%) remaining steroid free at 1 year. CONCLUSION: Short-term dose tailoring regains disease response in the majority of patients with CD. Of these, most will remain free of corticosteroids at 1 year after de-escalating therapy.

Compassionate access anti-tumour necrosis factor-α therapy for ulcerative colitis in Australia: the benefits to patients.

BACKGROUND: The efficacy of infliximab has been demonstrated in patients with both acute severe and moderate-severe ulcerative colitis (UC). However, there is a need for 'real-life data' to ensure that conclusions from trial settings are applicable in usual care. We therefore examined the national experience of anti-tumour necrosis factor-α (TNF-α) therapy in UC. METHODS: Case notes review of patients with UC who had received compassionate access (CA) anti-TNF-α therapy from prospectively maintained inflammatory bowel disease databases of six Australian adult teaching hospitals. RESULTS: Patients either received drug for acute severe UC (ASUC) failing steroids (n = 29) or for medically refractory UC (MRUC) (n = 35). In ASUC, the treating physicians judged that anti-TNF-α therapy was successful in 20/29 patients (69%); in these cases, anti-TNF-α was able to be discontinued (after 1-3 infusions in 19/20 responders) as clinical remission was achieved. Consistent with this perceived benefit, only 7/29 (24%) subsequently underwent colectomy during a median follow up of 12 months (interquartile range (IQR) 5-16). Eight of the 35 patients with MRUC (23%) required colectomy during a median follow up of 28 months (IQR 11-43). The majority of these patients (20/35 or 57%) had anti-TNF-α therapy for ≥4 months, whereas, 27/29 (93%) of ASUC patients had CA for ≤3 months. CONCLUSIONS: These data show an excellent overall benefit for anti-TNF-α therapy in both ASUC and MRUC. In particular, only short-duration anti-TNF-α was required in ASUC. These real-life data thus support the clinical trial data and should lead to broader use of this therapy in UC.

Practical guidelines for treating inflammatory bowel disease safely with anti-tumour necrosis factor therapy in Australia.

Anti-tumour necrosis factor (TNF) therapy is an effective but expensive option for treating inflammatory bowel disease (IBD). Its use is generally reserved for patients with severe refractory disease, often involving long-term administration. Anti-TNF therapy has the potential to be associated with various adverse effects, such as infection, malignancy and immunogenicity. Clinicians and patients should be familiar with these possibilities and adopt appropriate precautions prior to and during treatment to minimize risk. Guidelines have been developed for Australian prescribers intending to use anti-TNF therapy in IBD by a Working Party commissioned by IBD-Australia, a Special Interest Group affiliated with the Gastroenterology Society of Australia.

Randomised clinical trial: efficacy, safety and dosage of adjunctive allopurinol in azathioprine/mercaptopurine nonresponders (AAA Study).

BACKGROUND: Thiopurine hypermethylation towards 6-methylmercaptopurine (6MMP) instead of 6-thioguanine nucleotides (6TGN) is associated with inefficacy in patients with IBD. Allopurinol reverses such hypermethylation. AIMS: To prospectively determine efficacy of allopurinol-thiopurine combination and to compare 2 doses of allopurinol. DESIGN: In a multicentre, double-blind trial, patients with clinically active or steroid-dependent IBD and thiopurine shunting were randomised to 50 or 100 mg/d allopurinol and 25% of their screening thiopurine dose, which was subsequently optimised, aiming for 6TGN of 260-500 pmol/8x108 RBCs. The primary endpoint was steroid-free clinical remission at 24 weeks. RESULTS: Of 73 patients, 39 (53% [95% CI 42-65]) achieved steroid-free remission, (54% with 50 mg/d and 53% with 100 mg/d). 81% were able to discontinue steroids. Therapeutic 6TGN levels were achieved in both groups. Final thiopurine doses were lower with 100 mg/d allopurinol (P < 0.005). 6MMP: 6TGN ratio decreased from mean 64 to 4 (P < 0.001), being higher with 50 mg/d (6 ± 1.83) than for 100 mg/d ([1 ± 0.16], P = 0.003). Three patients on 50 mg/d failed to sustain low ratios at 24 weeks. Toxicity was minimal; three patients on 50 mg/d allopurinol developed transient leukopenia. Alanine aminotransferase concentrations decreased (P < 0.001) similarly in both arms. Faecal calprotectin levels at study end were lower in patients who achieved the primary endpoint (median 171 [85-541] vs 821[110-5892] ug/g, P = 0.03). CONCLUSIONS: Low-dose allopurinol-thiopurine combination safely reverses shunting and optimises 6TGN with associated improvement in disease activity. 100 mg/d allopurinol is preferable due to greater metabolite profile stability and lower thiopurine dose without additional toxicity.

Review article: appropriate use of corticosteroids in Crohn's disease.

BACKGROUND: Corticosteroids are a well-established treatment for active Crohn's disease and have been widely used for decades. It has become apparent, however, that a proportion of patients either fails to respond to corticosteroids or is unable to withdraw from them without relapsing. Furthermore, their use is associated with a range of side effects, such that long-term treatment carries unacceptable risk. AIM: To review the evidence regarding the appropriate use of corticosteroids in Crohn's disease, along with their side effects, safety and alternatives. METHODS: To collect relevant articles, a PubMed search was performed from 1966 to November 2006 using the terms 'steroid', 'corticosteroid', 'glucocorticoid', 'prednisolone', 'prednisone', 'methylprednisolone', 'hydrocortisone', 'dexamethasone' and 'budesonide' in combination with 'Crohn(s) disease'. Relevant articles were reviewed, as were their reference lists to identify further articles. RESULTS: When used correctly, corticosteroids are a highly effective, well tolerated, cheap and generally safe treatment for active Crohn' disease. Nevertheless, approximately 50% of recipients will either fail to respond (steroid-resistant) or will be steroid dependent at 1 year. Newer alternatives to corticosteroids are not, however, without risk themselves and, moreover, are not necessarily available universally. CONCLUSIONS: Steroids are used widely to treat Crohn's disease, a situation that is unlikely to change in the near future. Accordingly, efforts should be made to ensure that they are used correctly and that their side effects are minimized. Reference is made to recently published guidelines and a simplified 'users guide' is presented.

Intra-patient variability in adalimumab drug levels within and between cycles in Crohn's disease.

BACKGROUND: Whether therapeutic drug monitoring for adalimumab needs to be performed at trough has not been defined. AIM: To determine intra-patient adalimumab drug-level variation and to identify modulating patient and disease factors. METHODS: In this prospective observational study, adult patients with Crohn's disease established on maintenance adalimumab had drug levels measured repeatedly according to pre-defined schedules (visit 1: day 4-6, visit 2: day 7-9, trough: day 13-14) across two consecutive fortnightly cycles. Disease activity was assessed using Harvey-Bradshaw Index, C-reactive protein and faecal calprotectin. For this analysis, trough levels ≥4.9 µg/mL were considered therapeutic. RESULTS: Nineteen patients underwent 111 evaluations. Mean intra-patient drug levels from paired visits between cycles did not differ (visit1 cycle1: 4.81, cycle2: 5.21 µg/mL, P = 0.24, visit2 cycle1: 4.86, cycle2: 4.82, P = 0.91 and trough cycle1: 3.95, cycle2: 3.95, P = 0.99), irrespective of disease activity. Drug levels were stable over the first 9 days (visit 1-2), but declined to trough by a mean 1.06 and 0.89 µg/mL between visit 1 or 2, respectively (P < 0.001). Models using nontemporal factors (smoking, syringe delivery device) and levels at earlier visits accounted for 66-80% of the variance in trough levels. On receiver-operating curve analysis, thresholds identified in the first 9 days that predicted a therapeutic trough level were similar to the trough threshold itself, with high sensitivity but modest specificity. CONCLUSION: While therapeutic drug monitoring should be performed at trough, a drug level ≥4.9 µg/mL obtained during the first 9 days predicts a therapeutic trough drug level with reasonable confidence.

Review article: consensus statements on therapeutic drug monitoring of anti-tumour necrosis factor therapy in inflammatory bowel diseases.

BACKGROUND: Therapeutic drug monitoring (TDM) in inflammatory bowel disease (IBD) patients receiving anti-tumour necrosis factor (TNF) agents can help optimise outcomes. Consensus statements based on current evidence will help the development of treatment guidelines. AIM: To develop evidence-based consensus statements for TDM-guided anti-TNF therapy in IBD. METHODS: A committee of 25 Australian and international experts was assembled. The initial draft statements were produced following a systematic literature search. A modified Delphi technique was used with 3 iterations. Statements were modified according to anonymous voting and feedback at each iteration. Statements with 80% agreement without or with minor reservation were accepted. RESULTS: 22/24 statements met criteria for consensus. For anti-TNF agents, TDM should be performed upon treatment failure, following successful induction, when contemplating a drug holiday and periodically in clinical remission only when results would change management. To achieve clinical remission in luminal IBD, infliximab and adalimumab trough concentrations in the range of 3-8 and 5-12 µg/mL, respectively, were deemed appropriate. The range may differ for different disease phenotypes or treatment endpoints-such as fistulising disease or to achieve mucosal healing. In treatment failure, TDM may identify mechanisms to guide subsequent decision-making. In stable clinical response, TDM-guided dosing may avoid future relapse. Data indicate drug-tolerant anti-drug antibody assays do not offer an advantage over drug-sensitive assays. Further data are required prior to recommending TDM for non-anti-TNF biological agents. CONCLUSION: Consensus statements support the role of TDM in optimising anti-TNF agents to treat IBD, especially in situations of treatment failure.

The relevance of pharmacological dose--response curves to airway narrowing.

A defect in the smooth muscle of airways has been discarded as a possible cause of asthma in recent years because of the lack of correlation between airflow obstruction in patients and the contractile responsiveness of the isolated airway smooth muscle. Howard Mitchell and Malcolm Sparrow question the relevance of comparing parameters obtained from pharmacological dose-response curves (e.g. EC50) of strips of airways in vitro with those describing airways narrowing in vivo (e.g. resistance). They point out that in small airways the upper half of the dose-response curves seen in strips of airway wall is not represented in perfused tubular airway segments because they are fully constricted at or near the EC50 of the strip.

Allopurinol safely and effectively optimizes tioguanine metabolites in inflammatory bowel disease patients not responding to azathioprine and mercaptopurine.

BACKGROUND: Many non-responders to azathioprine or mercaptopurine (6-mercaptopurine) have high normal thiopurine methyltransferase activity and preferentially metabolize mercaptopurine to produce 6-methylmercaptopurine instead of the active 6-tioguanine (6-tioguanine) metabolites. AIM: To describe the use of allopurinol in mercaptopurine/azathioprine non-responders to deliberately shunt metabolism of mercaptopurine towards 6-tioguanine. METHODS: Fifteen thiopurine non-responders whose metabolites demonstrated preferential metabolism towards 6-methylmercaptopurine are described. Subjects were commenced on allopurinol 100 mg po daily and mercaptopurine/azathioprine was reduced to 25-50% of the original dose. Patients were followed clinically and with serial 6-tioguanine and 6-methylmercaptopurine metabolite measurements. RESULTS: After initiating allopurinol, 6-tioguanine levels increased from a mean of 185.73 +/- 17.7 to 385.4 +/- 41.5 pmol/8 x 10(8) red blood cells (P < 0.001), while 6-methylmercaptopurine decreased from a mean of 10 380 +/- 1245 to 1732 +/- 502 pmol/8 x 10(8) RBCs (P < 0.001). Allopurinol led to a decrease in white blood cell from a mean of 8.28 +/- 0.95 to 6.1 +/- 0.82 x 10(8)/L (P = 0.01). CONCLUSIONS: The addition of allopurinol to thiopurine non-responders with preferential shunting to 6-methylmercaptopurine metabolites appears to be an effective means to shift metabolism towards 6-tioguanine.

Systematic review: new serological markers (anti-glycan, anti-GP2, anti-GM-CSF Ab) in the prediction of IBD patient outcomes.

Traditionally, IBD diagnosis is based on clinical, radiological, endoscopic, and histological criteria. Biomarkers are needed in cases of uncertain diagnosis, or to predict disease course and therapeutic response. No guideline recommends the detection of antibodies (including ASCA and ANCA) for diagnosis or prognosis of IBD to date. However, many recent data suggest the potential role of new serological markers (anti-glycan (ACCA, ALCA, AMCA, anti-L and anti-C), anti-GP2 and anti-GM-CSF Ab). This review focuses on clinical utility of these new serological markers in diagnosis, prognosis and therapeutic monitoring of IBD. Literature review of anti-glycan, anti-GP2 and anti-GM-CSF Ab and their impact on diagnosis, prognosis and prediction of therapeutic response was performed in PubMed/MEDLINE up to June 2014. Anti-glycan, anti-GP2 and anti-GM-CSF Ab are especially associated with CD and seem to be correlated with complicated disease phenotypes even if results differ between studies. Although anti-glycan Ab and anti-GP2 Ab have low sensitivity in diagnosis of IBD, they could identify a small number of CD patients not detected by other tests such as ASCA. Anti-glycan Abs are associated with a progression to a more severe disease course and a higher risk for IBD-related surgery. Anti-GP2 Ab could particularly contribute to better stratify cases of pouchitis. Anti-GM-CSF Ab seems to be correlated with disease activity and could help predict relapses. These new promising biomarkers could particularly be useful in stratification of patients according to disease phenotype and risk of complications. They could be a valuable aid in prediction of disease course and therapeutic response but more prospective studies are needed.

Changes in myosin heavy chain stoichiometry in pig tracheal smooth muscle during development.

The stoichiometry of the myosin heavy chains (MHCs) has been measured in the tracheal smooth muscle of the pig after electrophoresis on SDS 4% polyacrylamide gel. The ratio of slower migrating MHC to the faster migrating MHC was 2.1 neonates, 1.5 in young and 0.95 in old pigs (P less than 0.01) showing that MHC composition changes with development. The unequal proportion of MHCs was not compatible with a heterodimeric arrangement of the MHCs in the native molecule as proposed earlier by Rovner et al. [(1986) Am. J. Physiol. 250, C861-870] and it is suggested that native molecules may be composed of homodimer heavy chains.

Modulation by the epithelium of the extent of bronchial narrowing produced by substances perfused through the lumen.

1 Airway narrowing was determined in vitro as a measure of bronchial reactivity. A bronchial segment from pig lung was perfused with a Krebs solution and the change in flow rate to drugs and small ions perfused intraluminally was compared with that obtained by application to the serosal surface. 2 The sensitivity (EC50) to acetylchloline was 30 times greater on the serosal surface than on the luminal surface. Concentrations of histamine and carbachol which had threshold responses on flow rate when perfused intraluminally virtually stopped flow on the serosal surface. Potassium depolarizing solutions (containing either KCl or K2SO4) and vanadate (VO3-) had little or no effect intraluminally but completely stopped flow through the bronchial segment when applied to the serosal surface, i.e. they closed off the airway. 3 After removal of the epithelium the sensitivity to drugs and K+ perfused intraluminally was increased to equal that on the serosal surface. 4 No evidence for suppression of smooth muscle contraction by a putative epithelium-derived inhibitory factor (EpDIF) could be obtained: no inhibition of smooth muscle contractility was seen when the agents listed above were perfused intraluminally and their perfusion continued while they were applied to outside. 5 It was concluded that the epithelium plays a crucial role as an impermeant barrier in modulating the responsiveness of the airways smooth muscle.

Mechanism of vanadate-induced contraction of airways smooth muscle of the guinea-pig.

The characteristics of vanadate-induced contraction of airways smooth muscle are described in isolated preparations of guinea-pig central and peripheral airways. Vanadate (1-1000 microM) induced sustained contractions of trachea and lung parenchymal strips within 1 min of challenge. It was more potent (P less than 0.001) on the lung strip (EC50 = 63 microM) than on the trachea (EC50 = 123 microM). The lung strip also developed greater maximum isometric tension (P less than 0.001) than the trachea. The efficacy on the lung strip was 2 and the trachea 0.6, relative to the response to acetylcholine (efficacy = 1). Vanadate-induced contractions of the trachea were not inhibited by atropine, mepyramine, phentolamine or indomethacin, nor after mast cell depletion by compound 48/80, showing that contractions were not mediated via specific receptors or by release of endogenous mediators of tone. Inorganic phosphate specifically inhibited vanadate responses in a dose-dependent and reversible manner, suggesting a common site of action. Contractions could be elicited in depolarized muscle and after treatment with ouabain plus propranolol, showing that membrane depolarization and inhibition of the Na, K-ATPase system were not involved in the contractile action of vanadate. Pretreatment of tracheal smooth muscle with verapamil had no influence on contractions elicited by vanadate. After removal of extracellular calcium, vanadate-induced contractions declined slowly with time, indicating that influx of extracellular calcium was not giving rise to contractions elicited by vanadate. Vanadate markedly increased the rate of calcium efflux from trachealis muscle loaded with 45Ca into both Ca2+-free and normal Krebs solutions; this is compatible with vanadate mobilizing an intracellular store of Ca2+. Such a store involving sites with Ca-ATPase activity would be consistent with the action of vanadate in isolated membrane preparations. Membrane-skinned tracheal fibres contracted by micromolar Ca2+ were relaxed by vanadate in a reversible dose-related manner, indicating that the contractile action of vanadate was not related to its interaction with proteins at the cross-bridge level.

The effect of catecholamines on the in vivo and in vitro responses of the cat lung during anaphylaxis.

1. Anaphylaxis in the lung of cats actively sensitized to Ascaris antigen has been investigated in vivo and in vitro. 2. In vivo there was a 100% increase in airways resistance and a 50% decrease in dynamic lung compliance following intravenous challenge with Ascaris antigen. Prostaglandin F2alpha induced similar changes but with histamine only dynamic lung compliance was affected. (-)-Isoprenaline prevented these prostaglandin F2alpha- and histamine-induced changes and caused a delay of about 2 min in the onset of the mechanical changes following anaphylactic challenge. 3. In vitro the isolated lung strip contracted within seconds of challenge whereas there was a delay of 2 to 3 min in the onset of the tracheal anaphylactic response. (-)-Isoprenaline, (-)-adrenaline and (+/-)-noradrenaline reduced the magnitude of anaphylactic contractions of the isolated trachea but did not significantly affect those of the isolated lung strip. This indicated lack of inhibition of mediator release from the lung parenchyma. 4. Histamine was released from sensitized lung fragments following challenge with the Ascaris extract. This release constituted 6.3% of the total tissue histamine and was not inhibited by (-)-isoprenaline (1 micrometer). 5. (-)-Isoprenaline abolished 5-hydroxytryptamine (5-HT)-induced contractions of the isolated trachea but not those elicited in response to acetylcholine. The isolated lung strip responses to histamine, prostaglandin F2alpha and 5-HT were highly resistant to inhibition by (-)-isoprenaline.

The cat lung strip as an in vitro preparation of peripheral airways: a comparison of beta-adrenoceptor agonists, autacoids and anaphylactic challenge on the lung strip and trachea.

1 A new in vitro preparation, the isolated lung strip of the cat, is described for investigating the direct effect of drugs on the smooth muscle of the peripheral airways of the lung. The preparation comprises a thin strip of lung parenchyma which can be mounted in a conventional organ bath for isometric tension recording. Its pharmacological responses have been characterized and compared with the isolated tracheal preparation of the cat. 2 The lung strip exhibited an intrinsic tone which was relaxed by catecholamines, aminophylline and flufenamate. It was contracted strongly by histamine, prostaglandin F2alpha, acetylcholine, compound 48/80, potassium depolarizing solution and alternating current field stimulation. In contrast, the cat trachea was unresponsive to histamine and prostaglandin F2alpha and did not exhibit an intrinsic tone. 3 (-)-Isoprenaline and (-)-adrenaline were much more potent in relaxing the lung strip than the trachea. The potency order of relaxation responses to isoprenaline, adrenaline and (+/-)-noradrenaline in the lung strip was isoprenaline greater than adrenaline greater than noradrenaline but in the trachea was isoprenaline greater than noradrenaline greater than or equal to adrenaline. 4 beta2-Adrenoceptor selective agonists salbutamol and terbutaline were more potent in the lung strip than the trachea, suggesting beta2-adrenoceptors predominated in the lung strip. Propranolol was equipotent in inhibiting isoprenaline relexations of the lung strip and trachea, whereas practolol was much less effective in inhibiting lung strip than trachea, further supporting a predominance of beta2-adrenoceptors in lung strip and beta1-adrenoceptors in trachea. 5 Strong Schultz-Dale type contractions were elicited in both lung strips and trachea by Ascaris lumbricoides antigen in actively sensitized cats. The initial phase of the contractile response of the lung strip following challenge was shown to be due to histamine release and was absent in the trachea. The delayed phase of the contraction which took several minutes to develop in both the mepyramine-treated lung strip and trachea was not due to prostaglandins E1, F2alpha or bradykinin, the probable mediator being slow reacting substance of anaphylaxis (SRS-A). 6 It is concluded that the isolated lung strip of the cat is useful as an in vitro model for investigating the effect of drugs on the smooth muscle of the peripheral airways of the lungs.

A comparison of the effects of polyarginine and stimulated eosinophils on the responsiveness of the bovine isovolumic bronchial segment preparation.

1. The bovine isovolumic bronchial segment preparation has been used to study the sensitivity and responsiveness of bronchial smooth muscle after various manipulations. 2. Addition of acetylcholine (ACh) to the lumen of the segments elicited an increase in intraluminal pressure as a result of contraction of the airway smooth muscle. However, the increases in intraluminal pressure were greater when the ACh was added to the adventitial surface of the preparation. 3. Addition of polyarginine to the bronchial lumen for 60-120 min resulted in an increased magnitude of response and greater than 100 fold increase in sensitivity to ACh administered into the lumen. Depolarizations induced by KCl were similarly enhanced when the solution was added into the lumen. In contrast, the sensitivity and responsiveness to ACh or K(+)-induced depolarization administered adventitially was unchanged. 4. The mechanical disruption of the epithelium produced a 32 fold increase in sensitivity to ACh introduced via the lumen, whereas the sensitivity to ACh added adventitially remained unaltered. 5. Addition of polyarginine to the adventitial bathing medium resulted in no change in the responsiveness or sensitivity to ACh, irrespective of whether the ACh was given intraluminally or adventitially. 6. Histological examination revealed that polyarginine caused extensive disordering of the normal architecture of the bronchial epithelium. Taken together with the unaltered responsiveness to adventitial ACh (i.e. lack of change in intrinsic muscle sensitivity) these observations suggest that the effect of polyarginine was most likely due to disruption of a diffusion barrier. 7. In contrast to the effects of polyarginine, the only effect of stimulated eosinophils was to produce a small diminution in the responsiveness to ACh that had been added adventitially.

Contraction of smooth muscle of pig airway tissues from before birth to maturity.

Two heavy chains of smooth muscle myosin (MHC1 and MHC2) were identified in pig airways and parenchyma. The ratio of MHC1 to MHC2 was the same along the bronchial tree in animals of the same age, but it changed with age (mature, young, suckling, and fetus), ranging from 0.8 in the mature to 2.2 in the fetus. Stress developed in airway (trachea, bronchus, and bronchiole) and parenchymal preparations in response to carbachol and histamine (mN/mm2) was normalized for myosin content (N/mm2 myosin). Airways from sucklings always developed the greatest stress to carbachol and histamine with the rank order of maximum force (Emax) suckling greater than fetus greater than young greater than mature for carbachol in large airways. Airway ranking to histamine was similar except that Emax of fetal bronchus and bronchiole were least. In parenchymal strips, mature animals gave strong responses to carbachol and histamine compared with other age groups. Sensitivity to carbachol was increased in the suckling trachea; otherwise it did not vary with age. Chemically skinned tracheal fibers exhibited three- to fourfold greater sensitivity to Ca2+ in fetal and suckling airways compared with the older animals. It is concluded that maturation of smooth muscle occurs in the expression of myosin, in the Ca2(+)-force relationships of the contractile machinery, and in the pharmacological responsiveness of the intact smooth muscle, with the latter greatest at or soon after birth.