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[Acute effect of inhaled beta(2)-agonists with different type of intrinsic activity on airway resistance in healthy volunteers].

Inhaled beta(2)-agonists (long-acting as well as short acting) are used world-wide for the relief of asthma symptoms. However, there are few reports which have evaluated the additive effect of short-acting beta(2)-agonists to long-acting beta(2)-agonists on airway resistance measured by a plethysmography. This study was designed to evaluate the additive effect of inhaled short-acting beta(2)-agonists (protecarol) to long-acting beta(2)-agonists (salmeterol) on airway resistance in normal healthy volunteers (S+P group). In addition, to compare the effects of beta(2)-agonists which have different types of intrinsic activities, acute effect of inhaled procaterol adding to procaterol was also evaluated (P+P group). Seven healthy volunteers (all male and all non-smokers) were entered in this study. Pulmonary function was measured by a body plethysmography. Forced expiratory volume per 1 second (FEV1), the maximum flow rate at 25% (V(.) 25), the maximum flow rate at 50% of forced vital capacity (V(.) 50), and airway resistance were measured before and after inhalation of salmeterol (1 dry powder, 50 microg) or procaterol (2 puffs, 20 microg). Sixty minutes after inhalation of salmeterol, or 15 minutes after inhalation of procaterol, inhalation of procaterol (2 puffs, 20 microg) was added, and then pulmonary function was monitored. FEV1, V(.) 25, and V(.) 50 were significantly increased after inhalation of salmeterol as well as procaterol. In addition, airway resistance decreased significantly after inhalation of salmeterol as well as procaterol. In the S+P group, additional decrease of airway resistance after inhalation of procaterol was relatively small compared with the P+P group. In conclusion, although additional bronchodilatoric effects were observed in the S+P and P+P group, the effects seemed to be different based on the intrinsic activity of each beta(2)-agonist.

Administration, Inhalation↗

Functional beta-adrenoceptors in the left atrium of normotensive and hypertensive rats.

1. The aim of the study was to characterize the functional beta 1-and beta 2-adrenoceptors of the rat left atrium and to investigate how these functional beta-adrenoceptor responses were altered in hypertension. The contractile responses of the left atrium from Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats to isoprenaline, T-0509 and procaterol were characterized. Subsequently, the effects of selective beta 1-(bisoprolol) and beta 2 (ICI 118,551)-adrenoceptor antagonists were investigated on these responses. 2. The maximal combined contractile responses of the rat left atrium to cardiac stimulation and CaCl2, isoprenaline, T-0509 or procaterol were not altered by hypertension. 3. The sensitivities to CaCl2 (pD2 on WKY left atrium = 2.99), isoprenaline (8.82) and T-0509 (8.84) were not altered by hypertension. There was an increase in sensitivity to procaterol from a pD2 value of 7.21 to 7.61 in the left atrium of the SH rat. 4. The basal tension induced by cardiac stimulation alone was inhibited by bisoprolol at > or = 10(-8) M and by ICI 118,551 at > or = 10(-7) M and this inhibitory effect is probably due to membrane stabilizing activity. 5. The pKB values for bisoprolol against isoprenaline, T-0509 and procaterol on the WKY were 8.43, 8.68 and 8.18, respectively, and were not different from SH rat left atrium. 6. The pKB value for ICI 118,551 against isoprenaline was increased from 7.06 on the WKY to 7.44 on the SH rat left atrium. The pKB values for ICI 118,551 against T-0509 and procaterol on the WKY were 7.18 and 8.14, respectively and were not significantly different from the SH rat left atrium values. 7. These results suggest that: (a) procaterol stimulates the beta 1-, in addition to, the beta 2-adrenoceptors of the rat left atrium; (b) functional beta 1-adrenoceptors are not altered in hypertension, and (c) there is probably an increase in the affinity of procaterol and isoprenaline for the beta 2-adrenoceptors which underlies the small increase in the functional beta 2-adrenoceptor response in hypertension.

Animals↗

Beta 2-adrenoceptors in guinea-pig atria.

The occurrence of beta 2-adrenoceptors in the isolated, spontaneously beating right atrium and the electrically driven left atrium of the guinea-pig was studied. Isoprenaline was used as reference compound and procaterol as selective beta 2-agonist. Cumulative concentration response (C/R) curves were obtained with the agonists. The C/R curve of procaterol was biphasic in both preparations. Compared with isoprenaline, procaterol was a partial agonist, with a mean maximum response of 0.78 +/- 0.04 in the right atrium and 0.29 +/- 0.05 in the left atrium. The beta 2-selective antagonist ICI 118,551, 10(-7) mol litre-1, caused a small but significant shift of the C/R curve of isoprenaline to a higher concentration range in both preparations. The same concentration of the beta 2-blocker changed the shape of the C/R curve of procaterol from biphasic to monophasic by blocking the responses to low concentrations of procaterol. Practolol, a beta 1-selective antagonist, 10(-6) mol litre-1, gave a highly significant shift of the C/R curve of isoprenaline to a higher concentration range in both preparations but had no effect on the responses to low concentrations of procaterol. The effect of practolol on the responses to high concentrations of procaterol is discussed. We conclude that the guinea-pig atria may contain beta 2-adrenoceptors mediating positive chronotropic and inotropic effects.

Animals↗

Probable involvement of vascular angiotensin II formation in the beta 2-adrenoceptor-mediated facilitation of the neurogenic vasopressor response in the pithed rat.

Rats were pithed, vagotomized and adrenalectomized and the effect of procaterol on the pressor response to electrical stimulation of the thoracolumbar preganglionic sympathetic outflow from the spinal cord or to exogenous noradrenaline was studied in the absence and presence of beta-adrenoceptor antagonists and drugs interfering with the renin-angiotensin system. 1. Basal diastolic blood pressure was decreased by captopril, ramiprilate (angiotensin converting enzyme inhibitors), saralasin (an angiotensin II receptor antagonist), pepstatin A (a protease inhibitor with renin antagonistic properties) and by functional nephrectomy (ligation of both renal hili), but was not affected by procaterol (a beta 2-adrenoceptor agonist), nebivolol (a beta 1-adrenoceptor antagonist) and ICI 118,551 (erythro-dl-1-(7-methylindan-4-yloxy)-3-isopropylaminobut an-2-ol; a beta 2-adrenoceptor antagonist). 2. The vasopressor response induced by electrical stimulation of the preganglionic sympathetic nerve fibres was increased by procaterol, whereas the increase in blood pressure evoked by exogenous noradrenaline was not affected. The pressor response to both electrical stimulation and exogenous noradrenaline was decreased by captopril, ramiprilate, saralasin and nephrectomy but was not affected by nebivolol and ICI 118,551. 3. The facilitatory effect of procaterol on the neurogenic, electrically induced pressor response, which was also obtained when basal blood pressure was decreased by nephrectomy and increased by Lys8-vasopressin, was abolished by ICI 118,551 but not affected by nebivolol. Under none of these experimental conditions did procaterol alter the vasopressor response to exogenous noradrenaline. 4. The facilitatory effect of procaterol on the neurogenic, electrically induced rise in blood pressure was abolished by captopril, ramiprilate, saralasin and pepstatin A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗

Different effects of beta-adrenoceptor desensitization on inhibitory actions in guinea-pig trachealis.

1. To determine the inhibitory effects of agents that pass through and bypass beta-adrenoceptors under conditions of tolerance to beta-adrenoceptor agonists, we examined the inhibition by the beta-adrenoceptor agonists forskolin and theophylline against contraction induced by methacholine (MCh) after exposure to higher concentrations of a beta-adrenoceptor agonist for a long time in guinea-pig tracheal smooth muscle, using isometric tension records. 2. After exposure to procaterol (0.0003-3 micromol/L) for 45 min, the inhibitory effect of 0.03 micromol/L procaterol on 1 micromol/L MCh-induced contraction was attenuated in a concentration-dependent manner, whereas after exposure to isoprenaline (0.0003-3 micromol/L) for an equivalent time, the inhibitory effect of isoprenaline was markedly attenuated at each concentration. However, after exposure to 3 micromol/L procaterol for 45 min, the inhibitory actions of forskolin and theophylline were, conversely, augmented. 3. These phenomena were observed under conditions whereby the response to MCh returned to control levels 6 h after removal of 3 micromol/L procaterol. The percentage inhibition produced by 0.1 micromol/L forskolin against 1 micromol/L MCh after exposure to normal bathing solution or 3 micromol/L procaterol for 45 min was 9.8 +/- 5.5 and 82.8 +/- 6.5%, respectively (P < 0.001). These values for 100 micromol/L (18 microg/mL) theophylline on MCh resposnes were 9.9 +/- 8.5 and 88.0 +/- 4.4% (n = 6 for both), respectively (P < 0.001). 4. The inhibitory action of agents that bypass beta-adrenoceptors was markedly augmented under conditions of beta-adrenoceptor desensitization in airway smooth muscle. 5. In conclusion, procaterol is less potent in causing desensitization of beta-adrenoceptors than isoprenaline. The activity of adenylyl cyclase may be enhanced after exposure to a high concentration of beta-adrenoceptor agonists.

Adrenergic beta-Agonists↗

Functional characterization of beta-adrenoceptor subtypes in the canine and rat lower urinary tract.

PURPOSE: We compared the effect of a beta 3-adrenoceptor (AR) agonist with that of beta 1 and beta 2-AR agonists on the urethra and bladder in the dog and rat. MATERIALS AND METHODS: In an in vitro experiment we studied the relaxant effect of subtype selective beta-AR agonists in canine and rat urethral and bladder smooth muscle using an organ bath method. In addition, in urethane anesthetized rats we measured urethral pressure and bladder pressure simultaneously in the presence of the beta 3-agonist CL316243 and the beta 2-agonist procaterol in 4 or 5 animals. RESULTS: In the dog the relaxing effects of isoprenaline in the distal urethra were about half those seen in the detrusor and trigone. The rank order of relaxing potency was CL316243 > dobutamine (beta 1-agonist) = procaterol in detrusor and trigone but procaterol > dobutamine = CL316243 in the prostatic and distal urethra. In rat urethral smooth muscle in vitro the corresponding order was procaterol > CL316243 > dobutamine and the maximal relaxation to each agonist was about half that seen in the bladder. In the anesthetized rat procaterol clearly decreased urethral pressure but CL316243 produced only a slight decrease at its maximal dose, although each agonists clearly reduced bladder pressure. The beta 2-antagonist ICI-118551 counteracted the decrease in urethral and bladder pressure induced by procaterol. CONCLUSIONS: In rats and dogs a selective beta 3-AR agonist can decrease bladder pressure without affecting urethral pressure.

Adrenergic beta-Agonists↗

Extracellular signal-regulated kinase 1/2 control Ca(2+)-independent force development in histamine-stimulated bovine tracheal smooth muscle.

The role of extracellular signal-regulated kinase (ERK)-1 and ERK-2 in controlling histamine-induced tone in bovine trachealis was investigated. PD 098059, an inhibitor of mitogen-activated protein kinase kinase (MKK)-1, had no effect on the histamine concentration-response relationship that described contraction. However, in the presence of EGTA, PD 098059 produced a parallel 5 fold rightwards shift of the histamine concentration-response curve without reducing the maximum response. The beta(2)-adrenoceptor agonist, procaterol, also displaced the histamine-concentration response curve to the right but the effect was much greater than that evoked by PD 098059, non-competitive and seen in the absence and presence of EGTA. A low basal level of pERK-1 and pERK-2 was always detected in untreated trachealis, which was significantly higher in EGTA-treated tissues and inhibited by PD 098059 and procaterol. Histamine markedly enhanced the phosphorylation of ERK-1 and ERK-2 by a mechanism that was also enhanced by EGTA and significantly attenuated by procaterol and PD 098059. Neither cholera toxin nor SP:-8-Br-cAMPS mimicked the ability of procaterol to dephosphorylate ERK. Similarly, neither pertussis toxin (PTX) nor RP:-8-Br-cAMPS, an inhibitor of cyclic AMP-dependent protein kinase (PKA), affected basal pERK levels or antagonized the inhibitory effect of procaterol. These data implicate the MKK-1/ERK signalling cascade in Ca(2+)-independent, histamine-induced contraction of bovine trachealis. In addition, the ability of procaterol to dephosphorylate ERK in an RP:-8-Br-cAMPS- and PTX-insensitive manner suggests that this may contribute to the anti-spasmogenic activity of beta(2)-adrenoceptor agonists by activating a novel PKA-independent pathway.

Animals↗

[Inhalation therapy for bronchial asthma. A. Bronchodilator--beta 2-stimulant].

In the treatment of bronchial asthma, usefulness of beta 2-agonists aerosol inhalation are emphasized as well as sustained theophylline tablets recently. In this study, the effectiveness of procaterol metered dose inhalor on asthmatic patients were examined compared with procaterol tables. The effect of procaterol inhalor together with sustained-theophylline on Holter ECG were also examined. When procaterol was exchanged to inhalation from tablets, 41% of the patients were improved symptomatically. Procaterol inhalor had no effect on Holter ECG. Procaterol inhalation regularly was expected to be more useful in treating asthmatic patients than tablets.

Administration, Inhalation↗

Beta adrenoceptors in the canine large coronary arteries: beta-1 adrenoceptors predominate in vasodilation.

Beta adrenoceptors of the canine large coronary artery were characterized by observing the effects of the subtype selective antagonists, metoprolol (beta-1) and ICI 118,551 (beta-2), on the vasodilator responses of isolated and perfused preparations to beta adrenoceptor agonists and in the radioligand binding assay. The integrity of the endothelium was checked by acetylcholine-induced vasodilations. Without any precontraction, isoproterenol, norepinephrine, epinephrine and procaterol (selective beta-2 agonist) dilated the canine large coronary artery pretreated with phentolamine (10(-5) M). The rank order of agonist potency was isoproterenol greater than norepinephrine greater than epinephrine greater than procaterol. The pA2 values for metoprolol and ICI 118,551 were determined by the antagonisms of the vasodilator responses to isoproterenol and procaterol. The slopes of Schild plots for metoprolol and ICI 118,551 against isoproterenol and the value for ICI 118,551 against procaterol were not significantly different from unity, but the value for metoprolol against procaterol was significantly less than unity. The pA2 value for metoprolol against isoproterenol was 7.48 and those values for ICI 118,551 against isoproterenol and procaterol was 7.19 and 7.25, respectively. These pA2 values are typical for beta-1 adrenoceptors. The beta adrenoceptors of the canine large coronary artery were examined further using an antagonist [125I]iodocyanopindolol as a ligand for the binding of beta adrenoceptors. The [125I]iodocyanopindolol binding to the canine coronary artery smooth muscle membrane was saturable with a KD of 63.7 pM and a total number of radioligand binding sites of 44 fmol/mg of protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗

Inhibition by fenoterol of human eosinophil functions including beta2-adrenoceptor-independent actions.

Agonists at beta2 adrenoceptors are used widely as bronchodilators in treating bronchial asthma. These agents also may have important anti-inflammatory effects on eosinophils in asthma. We examined whether widely prescribed beta2-adrenoceptor agonists differ in ability to suppress stimulus-induced eosinophil effector functions such as superoxide anion (O2-) generation and degranulation. To examine involvement of cellular adhesion in such responses, we also investigated effects of beta2 agonists on cellular adhesion and on CD11b expression by human eosinophils. O2- was measured using chemiluminescence. Eosinophil degranulation and adhesion were assessed by a radioimmunoassay for eosinophil protein X (EPX). CD11b expression was measured by flow cytometry. Fenoterol inhibited platelet-activating factor (PAF)-induced O2- generation by eosinophils significantly more than salbutamol or procaterol. Fenoterol partially inhibited PAF-induced degranulation by eosinophils similarly to salbutamol or procaterol. Fenoterol inhibited phorbol myristate acetate (PMA)-induced O2- generation and degranulation by eosinophils, while salbutamol or procaterol did not. Fenoterol inhibition of PMA-induced O2- generation was not reversed by ICI-118551, a selective beta2-adrenoceptor antagonist. Fenoterol, but not salbutamol or procaterol, significantly inhibited PAF-induced eosinophil adhesion. Fenoterol inhibited O2- generation and degranulation more effectively than salbutamol or procaterol; these effects may include a component involving cellular adhesion. Inhibition also might include a component not mediated via beta2 adrenoceptors.

Adrenergic beta-Agonists↗