Causas de Morte em Doentes com Hemofilia: Estudo Retrospectivo de 1979 a 2007, no Serviço de Imunohemoterapia do HSJ

Neurokinin A (NKA) induces bronchoconstriction mediated by tachykinin NK2 receptors in animals and humans, and may be increased in asthma. Because beta(2)-adrenoceptor agonists are the most widely used bronchodilators in asthma, we investigated the effects of the beta(2)-adrenoceptor agonist fenoterol on NK2 receptor messenger RNA (mRNA) and receptor density as well as the functional responses of bovine tracheal smooth muscle to the NK2 receptor agonist [beta-Ala(8)]-NKA(4-10) in vitro, using Northern blot analysis, receptor binding, and organ bath studies. Incubation with fenoterol induced a time- and concentration-dependent upregulation of NK2 receptor mRNA (71% increase after 12 h at 10(-7) M fenoterol), which was abolished by propranolol (a nonselective beta-adrenoceptor agonist) and ICI118551 (a selective beta(2)-adrenoceptor antagonist), but not by CGP20712A (a selective beta(1)-adrenoceptor antagonist), indicating that fenoterol acts via beta(2)-adrenoceptors. These effects were mimicked by forskolin and prostaglandin E-2 (PGE,), both agents that increase cyclic adenosine monophosphate (cAMP), and by the cAMP analogue 8-bromo-cAMP. The upregulation was blocked by cycloheximide, indicating that it requires new protein synthesis, and was accompanied by an increase in both the stability of NK2 receptor mRNA and the rate of NK2 receptor gene transcription. Radioligand binding assay using the selective NK2 receptor antagonist [H-3]SR48968 showed a significant increase in the number of receptor binding sites after 12 h and 18 h, which was accompanied by an increased contractile responsiveness to the NK2 receptor agonist [beta-Ala(8)]-NKA(4-10). Dexamethasone completely prevented the fenoterol-induced increase in NK2 receptor mRNA and in the contractile response. We conclude that beta(2)-adrenoceptor agonists induce upregulation of functional NK2 receptors in airway smooth muscle by increasing cAMP, and that this can be prevented by a corticosteroid. The increased responsiveness could be relevant to asthma control and mortality

Characterization of the muscarinic receptor subtype involved in phosphoinositide metabolism in bovine tracheal smooth muscle.

1. The muscarinic receptor subtype involved in the methacholine-induced enhancement of phosphoinositide metabolism in bovine tracheal smooth muscle was identified by using the M2-selective antagonist AF-DX 116 and the M3-selective antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) methobromide, in addition to the M1-selective antagonist pirenzepine, in a classical Schild analysis. 2. All the antagonists shifted the methacholine dose-response curve to the right in a parallel and concentration-dependent fashion, yielding Schild plots with slopes not significantly different from unity. The pA2 values (6.94, 6.32 and 8.54 for pirenzepine, AF-DX 116 and 4-DAMP methobromide respectively) indicate that it is the M3 (smooth muscle/glandular), but not the M2 (cardiac) muscarinic receptor subtype, present in this tissue, that mediates phosphoinositide turnover, in accordance with our previous contractile studies. 3. The results provide additional evidence for the involvement of phosphoinositide turnover in the pharmacomechanical coupling between muscarinic receptor stimulation and contraction in (bovine tracheal) smooth muscle

Characterization of presynaptic vascular muscarinic receptors inhibiting endogenous noradrenaline overflow in the portal vein of the freely moving rat.

1. In the portal vein of permanently cannulated, freely moving, unanaesthetized rats, methacholine (MCh) is able to inhibit the electrically-evoked endogenous noradrenaline (NA) overflow. This inhibition is mediated by presynaptic inhibitory muscarinic heteroreceptors. 2. By use of pirenzepine, 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP) and AF-DX 116 as M1-, M3-, and M2-selective antagonists respectively, the MCh (0.1 microM)-induced inhibition of the electrically-evoked NA overflow could be reversed to the control stimulation value dose-dependently. 3. The potency order of the antagonists was: 4-DAMP greater than AF-DX 116 greater than pirenzepine, pIC50 values being 8.50, 7.96 and 7.01, respectively. 4. From these results it was concluded that the inhibitory presynaptic heteroreceptors in the portal vein of conscious unrestrained rats are of the cardiac M2-subtype

Dysfunction of muscarinic M2 receptors after the early allergic reaction: possible contribution to bronchial hyperresponsiveness in allergic guinea-pigs.

1. Using a guinea-pig model of allergic asthma, in which the animals display early (0-5 h) and late phase (8-23 h after antigen challenge) bronchoconstrictor reactions, the function of prejunctional inhibitory M2 and postjunctional M3 receptors in isolated tracheal preparations have been investigated. In addition, cardiac M2 receptor function in vitro and bronchial responsiveness to histamine in vivo were evaluated. 2. Sensitivity to inhaled histamine was increased 3.1 fold and 1.6 fold after the early and late allergic reactions (i.e. at 5 h and 23 h after a single ovalbumin challenge), respectively. At 23 h after the last of four allergen challenges, executed on four consecutive days, bronchial hyperresponsiveness to histamine was diminished to 1.3 fold. 3. After the early response, there was no change in cardiac muscarinic M2 receptor function, since in left atria pD2 (-log EC50) and Emax values of pilocarpine and pKB values of AQ-RA 741, a selective M2 receptor antagonist, were not significantly different from controls (unchallenged sensitized animals), and this also applied to methacholine pD2 values for muscarinic M3 receptors in tracheal smooth muscle. 4. Prejunctional inhibitory muscarinic M2 autoreceptors in airway smooth muscle were markedly dysfunctional after the early allergic response, since potentiation of electrically evoked twitch contractions of tracheal preparations by low concentrations of the M2-selective muscarinic receptor antagonists, gallamine, methoctramine, AQ-RA 741 and AF-DX 116, which is the result of M2 receptor blockade, was clearly and significantly diminished compared to controls.(ABSTRACT TRUNCATED AT 250 WORDS

Contribution of a cholinergic reflex mechanism to allergen-induced bronchial hyperreactivity in permanently instrumented, unrestrained guinea-pigs.

1. In conscious, permanently instrumented, unrestrained, ovalbumin-sensitized guinea-pigs the development of allergen-induced bronchial hyperreactivity to histamine- and methacholine-inhalation was investigated after the early as well as after the late asthmatic response. 2. The allergen-induced increase in bronchial reactivity to histamine was significantly higher than to methacholine. 3. The muscarinic receptor antagonist, ipratropium bromide (1.0 mM, 3 min inhalation), blocked methacholine-induced bronchoconstriction and caused a significant 1.7 fold inhibition of the histamine-induced bronchoconstriction of control animals. 4. A lower dose of ipratropium bromide (0.1 mM, 3 min inhalation) had no significant effect on histamine-induced bronchoconstriction in control animals, but significantly reduced the allergen-induced increase in bronchial reactivity to histamine between the early and late asthmatic response. At 1.0 mM ipratropium bromide, no further reduction was observed. 5. These results clearly indicate that an exaggerated cholinergic reflex mechanism contributes to allergen-induced bronchial hyperreactivity to histamine

Isolated porcine bronchi provide a reliable model for development of bronchodilator anti-muscarinic agents for human use

Background and purpose: In human airways, muscarinic acetylcholine receptors (mAChRs) exert a predominant role in the control of airways resistance and anti-muscarinic agents are currently included in the pharmacological treatment of chronic obstructive pulmonary disease (COPD). However, the development of more effective mAChR antagonists is hampered by considerable species variability in the ultrastrucural and functional control of airway smooth muscle, making extrapolation of any particular animal model questionable. This study was designed to characterize the mAChRs in a bronchial preparation from pigs, animals considered to provide close models of human biology