Effects of fenoterol on beta-adrenoceptor and muscarinic M2 receptor function in bovine tracheal smooth muscle.
Eur J Pharmacol
; 419(2-3): 253-9, 2001 May 11.
Article
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| MEDLINE
| ID: mdl-11426849
ABSTRACT
Prolonged (18 h) incubation of isolated bovine tracheal smooth muscle with the beta2-adrenoceptor agonist fenoterol (10 microM) induced desensitization of isoprenaline-induced adenylyl cyclase activity in bovine tracheal smooth muscle membranes, characterized by a 25% decrease in maximal effect (Emax) (P < 0.05), while the sensitivity to the agonist (pEC50) was unchanged. The Emax value of isoprenaline-induced smooth muscle relaxation of submaximal methacholine-induced contractile tones was similarly reduced by about 25% (P < 0.001), while the pEC50 value was diminished by 1.0 log unit (P < 0.001). As determined by 30 microM gallamine-induced muscarinic M2 receptor antagonism and pertussis toxin-induced inactivation of G(i alpha), muscarinic M2 receptor-mediated functional antagonism did not play a role in isoprenaline-induced relaxation of bovine tracheal smooth muscle contracted by methacholine, both in control and in 18-h fenoterol-treated tissue. In line with these observations, we found no enhanced muscarinic M2 receptor-mediated inhibition of 1 microM forskolin-stimulated adenylyl cyclase activity after 18-h fenoterol treatment. These data indicate that 18-h fenoterol treatment of bovine tracheal smooth muscle induces beta2-adrenoceptor desensitization and reduced functional antagonism of methacholine-induced contraction by beta-adrenoceptor agonists, without a change of muscarinic M2 receptor function.
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Base de datos:
MEDLINE
Asunto principal:
Receptores Adrenérgicos beta
/
Receptores Muscarínicos
/
Agonistas Adrenérgicos beta
/
Fenoterol
/
Músculo Liso
Idioma:
En
Revista:
Eur J Pharmacol
Año:
2001
Tipo del documento:
Article