title: Magnesium-calcium signalling in rat parotid acinar cells: effects of acetylcholine.
abstract: This study investigated the effects of extracellular Mg(2+) ([Mg(2+)](o)) on basal and acetylcholine (ACh)-evoked amylase secretion and intracellular free Ca(2+) ([Ca(2+)](i)) in rat parotid acinar cells. In a medium containing 1.1 mM [Mg(2+)](o), ACh evoked significant increases in amylase secretion and [Ca(2+)](i). Either low (0 mM) or elevated (5 and 10 mM) [Mg(2+)](o) attenuated ACh-evoked responses. In a nominally Ca(2+) free medium, elevated [Mg(2+)](o) attenuated basal and ACh-evoked amylase secretion and [Ca(2+)](i). In parotid acinar cells incubated with either 0, 1.1, 5 or 10 mM [Mg(2+)](o), ACh evoked a gradual decrease in [Mg(2+)](i). These results indicate that the ACh-evoked Mg(2+) efflux is an active process since Mg(2+) has to move against its gradient. Either lidocaine, amiloride, N-methyl-D: -glucamine, quinidine, dinitrophenol or bumetanide can elevate [Mg(2+)](i) above basal level. In the presence of these membrane transport inhibitors, ACh still evoked a decrease in [Mg(2+)](i) but the response was less pronounced with either [Na(+)](o) removal or in the presence of either amiloride or quinidine. These results indicate marked interactions between Ca(2+) and Mg(2+) signalling in parotid acinar cells and that ACh-evoked Mg(2+) transport was not dependent upon [Na(+)](o).
authors.affiliation: Department of Oral Biology, Faculty of Dental Medicine, University of Lisbon, Cidade Universitária, Lisboa, Portugal.
authors.forename: Antonio
authors.initials: A
authors.lastname: Mata
authors.forename: Duarte
authors.initials: D
authors.lastname: Marques
authors.forename: María A
authors.initials: MA
authors.lastname: Martínez-Burgos
authors.forename: João
authors.initials: J
authors.lastname: Silveira
authors.forename: Joana
authors.initials: J
authors.lastname: Marques
authors.forename: Maria F
authors.initials: MF
authors.lastname: Mesquita
authors.forename: José A
authors.initials: JA
authors.lastname: Pariente
authors.forename: Gines M
authors.initials: GM
authors.lastname: Salido
authors.forename: Jaipaul
authors.initials: J
authors.lastname: Singh
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000681:Amylases / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D005260:Female; D008274:Magnesium / Q000378:metabolism / Q000493:pharmacokinetics / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D010306:Parotid Gland / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D000681:Amylases; D008274:Magnesium; D000109:Acetylcholine; D002118:Calcium