title: The calcium dependency of mucus glycoconjugate secretion by canine tracheal explants.
abstract: Canine tracheal explants, incubated overnight with [14C]-glucosamine, elicited an enhanced secretion of ethanol-precipitated 14C-labelled glycoconjugate when challenged with methacholine, 10 microM. Explants were rendered deficient in total calcium content and unresponsive to methacholine, 10 microM, by incubating them in calcium-free medium for 18 to 22 h; however, the secretory response to the cholinergic agonist was restored with the addition of calcium to the medium. A dose-response relationship resulted when explants were challenged with methacholine in nutrient medium containing varied calcium concentrations (0.45 to 7.2 mM); alterations in the calcium concentration in the absence of methacholine had no significant effect on the basal secretion of 14C-labelled glycoconjugate. The calcium-selective ionophore A23187, 10 microM, stimulated [14C]-glycoconjugate secretion and induced the most significant effect in the presence of nutrient medium containing calcium. Verapamil, 10 microM, a calcium-entry blocker failed to inhibit basal or stimulated [14C]-glycoconjugate secretion; however, the intracellular calcium antagonist TMB-8, 10 to 100 microM, inhibited methacholine-induced [14C]-glycoconjugate secretion in a dose-dependent manner. These data suggest that respiratory mucus secretion is a calcium-dependent process and that intracellular calcium is more vital than extracellular calcium in supporting this phenomenon.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D004285:Dogs; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008688:Methacholine Compounds / Q000494:pharmacology; D009092:Mucous Membrane / Q000378:metabolism; D009093:Mucus / Q000378:metabolism*; D014132:Trachea / Q000378:metabolism* / Q000637:transplantation; D014700:Verapamil / Q000494:pharmacology
chemical_list: D008688:Methacholine Compounds; D000001:Calcimycin; D000431:Ethanol; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D014700:Verapamil; D002122:Calcium Chloride; D002118:Calcium