title: Influence of epithelium and isoprenaline incubation on responsiveness of guinea-pig trachea to methacholine.
abstract: There are reports regarding harmful effect of long-term use of beta2-agonist drugs on asthma severity and airway responsiveness. In the present study, the responses of guinea pig trachea with intact and denuded epithelium (groups 1 and 2, n = 10) to methacholine as EC50 were measured in tissues nonincubated or incubated with 10 mumol/l isoprenaline during the resting period. The same protocol was performed in groups 3 and 4 (n = 5 for each group) with an additional 30 min rest time after isoprenaline incubation. The response of trachea with denuded epithelium (groups 2 and 4) to methacholine was significantly higher than that with intact epithelium both in incubated and nonincubated conditions (groups 1 and 3, p < 0.05 to p < 0.001). Incubation with isoprenaline caused a significant reduction in the tracheal response to methacholine in both the denuded groups (p < 0.005 and p < 0.001) and intact epithelium groups (p < 0.005 for both cases). The reduction in tracheal responsiveness to methacholine due to incubation in epithelium denuded trachea (groups 2 and 4) was nonsignificantly greater than that of intact epithelium tissues. There was no difference between groups 3 and 4 with those of groups 1 and 2 in both incubated and non incubated conditions. The maximum contractility response to methacholine was not different between tracheal chains with denuded and intact epithelium and did not change due to incubation with isoprenaline. The results of this study indicate reduction of tracheal response to methacholine due to incubation of tissues with isoprenaline, which was relatively more pronounced in epithelium denuded trachea.
authors.affiliation: Department of Physiology, Ghaem Medical Centre, Mashhad University of Medical Sciences, Mashhad, Iran. mhboskabady@hotmail.com
authors.forename: M H
authors.initials: MH
authors.lastname: Boskabady
authors.forename: M R
authors.initials: MR
authors.lastname: Aslani
authors.forename: A
authors.initials: A
authors.lastname: Tabatabaei
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000139:chemically induced; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D001993:Bronchodilator Agents / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D014132:Trachea / Q000187:drug effects* / Q000502:physiology / Q000503:physiopathology
chemical_list: D000318:Adrenergic beta-Agonists; D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D016210:Methacholine Chloride; D007545:Isoproterenol