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

Canine tracheal explants, incubated overnight with [3H]glucosamine, elicited an enhanced secretion of ethanol-precipitated [3H]labelled glycoconjugate when challenged with methacholine, 10 microM. Neither the beta-adrenoceptor agonist isoprenaline, 10 microM, 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 microM, stimulated [3H]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.