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Microfluorometric studies of intracellular Ca2+ and Na+ concentrations in normal human labial gland acini

Abstract : The responses of human labial salivary acini to muscarinic, adrenergic, and substance P peptidergic stimulation were studied using the fluorescent indicators fura 2 for intracellular Ca2+ concentration ([Ca2+]i) and sodium-binding benzofuran isophthalate for intracellular Na+ concentration ([Na+]i). Of the agents tested (carbachol, epinephrine, isoproterenol, and substance P) only the muscarinic agonist carbachol increased [Ca2+]i substantially above basal levels (three to fourfold; half-maximal effect approximatley 1 microM). Experiments with the Ca(2+)-adenosinetriphosphatase inhibitor thapsigargin indicated the presence of both thapsigargin-sensitive and thapsigargin-insensitive intracellular Ca2+ stores, both of which were mobilized by carbachol. [Na+]i in resting labial acini was approximately 20 mM. On stimulation with carbachol, [Na+]i rose transiently to more than three times this value and then partially recovered. This carbachol-induced rise in [Na+]i was largely blocked by bumetanide, a specific inhibitor of the Na(+)-K(+)-2Cl- cotransporter. These results are consistent with an intact muscarinic fluid secretory response in human labial acini with transepithelial Cl- secretion driven via Na(+)-K(+)-2Cl- cotransport and the secretion of fluid presumably following Cl- loss via an apical Ca(2+)-dependent anion channel, as observed in salivary acini from other species.
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I. Valdez, M. Paulais, P. Fox, R. Turner. Microfluorometric studies of intracellular Ca2+ and Na+ concentrations in normal human labial gland acini. AJP - Gastrointestinal and Liver Physiology, American Physiological Society, 1994, 267 (4), pp.G601-G607. ⟨10.1152/ajpgi.1994.267.4.G601⟩. ⟨inserm-02448224⟩



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