Resting tension effect on airway smooth muscle: the involvement of epithelium.
We studied the influence of resting tension (RT) on rabbit tracheal smooth muscle (TSM) contractions induced by acetylcholine or KCl as well as the role of epithelium and the endogenously produced nitric oxide, prostanoids and endothelin on these responses. The alteration of RT from 0.5 to 2.5 g increased the responsiveness of TSM to KCl. The presence of atropine decreased KCl-induced contractions obtained only at 2.5 g RT. The removal of epithelium increased acetylcholine-induced contractions, only at 2.5 g RT. At 0.5 g RT, the presence of L-NAME had no effect on acetylcholine-induced contractions while indomethacin decreased contractions induced by 10(-3) M acetylcholine. At 2.5 g RT, the presence of L-NAME increased acetylcholine-induced contractions while indomethacin, BQ-123 and BQ-788 had no effect. These results demonstrate that RT affects the responsiveness of TSM differentially, depending on the agonist or integrity of the epithelium. Airway epithelium modulates acetylcholine-induced contractions, only at 2.5 g RT partly via NO release. At 0.5 g RT, the endogenous production of prostanoids by sources other than epithelium modulates the contractility of TSM to acetylcholine.
Hatziefthimiou
Apostolia A
AA
Department of Physiology, Medical School, University of Thessaly, Papakiriazi 22, 41222 Larissa, Greece. axatzi@med.uth.gr
Karetsi
Eleni
E
Pratzoudis
Evripidis
E
Gourgoulianis
Konstantinos I
KI
Molyvdas
Paschalis-Adam
PA
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D020545:Respiratory Mucosa / Q000502:physiology*; D014132:Trachea / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*
D004791:Enzyme Inhibitors; D011189:Potassium Chloride; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester