Cyclic nucleotides fail to affect mucus glycoconjugate secretion from canine tracheal explants

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Abstract
Canine tracheal explants, incubated overnight with [3 H]glucosamine, elicited an enhanced secretion of ethanol-precipitated [3 H]labelled glycoconjugate when challenged with methacholine, 10 μM. Neither the β-adrenoceptor agonist isoprenaline, 10 μM, nor the phosphodiesterase inhibitor theophylline, 10 mM, had any significant effect on glycoconjugate secretion. Dibutyryl cyclic AMP, 1 mM, and dibutyryl cyclic GMP, 1 mM, alone or in combination with theophylline, 10 mM, were devoid of activity on unstimulated or methacholine-stimulated tracheal explants. The calcium ionophore A23187, 10 μM, stimulated [3 H]glycoconjugate secretion from each of the tissues tested; however, the cyclic nucleotides failed to modify this response. These data indicate that the cyclic nucleotides play little, if any, role in mucus glycoconjugate secretion by the canine trachea.