We measured the intracellular free calcium ion concentration ([Ca2+](i)) of acinar cells in isolated feline tracheal submucosal glands in response to secretagogues using the Ca2+-sensitive fluorescent dye fura-2. The secretagogues included cholinergic, adrenergic agonists, substance P (SP), and vasoactive intestinal polypeptide (VIP) which induce mucus glycoprotein secretion from feline tracheal submucosal glands. Methacholine (MCh) produced a significant increase in [Ca2+](i) of up to 9.8 times that of control in a dose-dependent fashion at concentrations of 10-8 to 10-3 M. [Ca2+](i) increase by MCh reached a peak within 30 s after stimulation and thereafter showed a sustained rise. In Ca2+-free medium, MCh produced an initial transient rise, which was <30% of that in a Ca2+-containing solution, and which lasted for 60 s with no prolonged sustained rise in [Ca2+](i). Atropine abolished MCh-evoked [Ca2+](i) increase. Phenylephrine and SP produced a prolonged increase in [Ca2+](i) without an initial transient increase. Phenylephrine (up to 10-4 M) evoked an increase in [Ca2+](i) by up to 240% that of control, which was abolished by prazosin. SP (up to 10-4 M) also evoked an increase in [Ca2+](i) by 155% that of control, which was abolished by atropine. By contrast, both isoproterenol (up to 10-5 M) and VIP (up to 10-5 M) failed to alter [Ca2+](i). These findings indicate that the mucus glycoprotein secretion evoked by muscarinic cholinergic, α-adrenergic agonist or SP can be mediated by intracellular Ca2+, whereas that by β-adrenergic agonists or VIP cannot.
|ジャーナル||American Journal of Physiology - Lung Cellular and Molecular Physiology|
|出版ステータス||Published - 1990|
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