title: Signal transduction pathways in modulation of ciliary beat frequency by methacholine.
abstract: The release of endogenous neurotransmitters plays an important role in the airway mucosal defense system. We studied the in vitro effect of methacholine, a beta-methyl ester of acetylcholine, on the ciliary beat frequency (CBF) of human adenoid explants and its mechanism of action. Tissue explants were cultured at 35 degrees C and covered with 1.0 mL of culture medium: minimum essential Eagle's medium (MEM) containing L-arginine (1.2 x 10(-3) mol/L). Methacholine was added to the cultured tissue at concentrations of 10(-10), 10(-8), and 10(-6) mol/L. The CBF was determined by phase contrast microscopy and microphotometry. Methacholine increased CBF in a dose-dependent manner with a maximum increase of 23.0% +/- 1.8% (p < .001). Atropine (10(-6) mol/L) significantly inhibited the ciliostimulatory effects of methacholine (p < .0007). The role of endogenous prostaglandins in methacholine-induced ciliostimulation was determined by treating specimens with a cyclooxygenase inhibitor (diclofenac sodium). Diclofenac (10(-6) mol/L) significantly inhibited the ciliostimulatory effects of methacholine (p < .0007). To determine if nitric oxide (NO) acts as an intermediary in ciliostimulation by methacholine, endogenous NO production was inhibited by treating specimens with an L-arginine analog, NG-nitro-L-arginine methyl ester (L-NAME), prior to addition of methacholine. L-NAME (10(-6) mol/L) inhibited the effects of methacholine in L-arginine-free MEM (p < .008), and this inhibition was reversed by L-arginine (10(-3) mol/L). To further examine the actions of NO in methacholine-induced ciliostimulation, a cyclic guanosine 3'5'-monophosphate (cGMP) kinase inhibitor (KT-5823) was used, prior to the addition of methacholine. KT-5823 (10(-6) mol/L) significantly inhibited the effects of methacholine (p < .0001). Ciliostimulation by methacholine in human upper airway mucosa involves both prostaglandin and NO second messengers and activation of a cGMP-dependent kinase.
authors.affiliation: Department of Otorhinolaryngology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: B
authors.initials: B
authors.lastname: Yang
authors.forename: R J
authors.initials: RJ
authors.lastname: Schlosser
authors.forename: T V
authors.initials: TV
authors.lastname: McCaffrey
mesh_terms: D000109:Acetylcholine / Q000502:physiology; D000234:Adenoids / Q000187:drug effects / Q000502:physiology; D001285:Atropine / Q000494:pharmacology; D002923:Cilia / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D016210:Methacholine Chloride / Q000494:pharmacology*; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009297:Nasal Mucosa / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology; D010277:Parasympathomimetics / Q000494:pharmacology*; D011453:Prostaglandins / Q000502:physiology; D015290:Second Messenger Systems / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D010277:Parasympathomimetics; D011453:Prostaglandins; D016210:Methacholine Chloride; D009569:Nitric Oxide; D001285:Atropine; D000242:Cyclic AMP; D006152:Cyclic GMP; D000109:Acetylcholine