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Effect of extracellular magnesium on nerve-mediated and acetylcholine-evoked in vitro amylase release in rat parotid gland tissue

Published online by Cambridge University Press:  21 May 2002

M. D. Yago ,
A. D. Mata ,
M. Mañas  and
J. Singh
M. D. Yago
Affiliation:
Institute of Nutrition and Food Technology, Department of Physiology, University of Granada, 18071 Granada, Spain, Department of Oral Biology, ISCS-Sul, 2825 Monte de Caparica, Portugal and Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK
A. D. Mata
Affiliation:
Institute of Nutrition and Food Technology, Department of Physiology, University of Granada, 18071 Granada, Spain, Department of Oral Biology, ISCS-Sul, 2825 Monte de Caparica, Portugal and Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK
M. Mañas
Affiliation:
Institute of Nutrition and Food Technology, Department of Physiology, University of Granada, 18071 Granada, Spain, Department of Oral Biology, ISCS-Sul, 2825 Monte de Caparica, Portugal and Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK
J. Singh
Affiliation:
Institute of Nutrition and Food Technology, Department of Physiology, University of Granada, 18071 Granada, Spain, Department of Oral Biology, ISCS-Sul, 2825 Monte de Caparica, Portugal and Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK
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Abstract

In this study the effects of changes in extracellular magnesium ([Mg2+]o) and calcium ([Ca2+]o) concentrations on basal and on nerve-mediated and acetylcholine (ACh)-evoked in vitro amylase release and calcium mobilization were investigated in rat parotid gland tissue. In the presence of a normal (2.56 mM) [Ca2+]o, both zero (0 mM) and an elevated (10 mM) [Mg2+]o significantly attenuated basal and ACh-evoked amylase release compared to the response obtained in normal (1.1 mM) [Mg2+]o. During electrical field stimulation (EFS) of parotid tissues, only elevated [Mg2+]o reduced amylase release. In a Ca2+-free medium, both basal and ACh-evoked amylase output were markedly reduced compared to the responses obtained under similar conditions in normal [Ca2+]o. Again, the ACh-induced amylase release in a Ca2+-free solution was larger in normal [Mg2+]o than when the [Mg2+]o was either zero or was elevated to 10 mM. Perturbation of [Mg2+]o had no significant effect on basal intracellular free calcium concentration ([Ca2+]i) in parotid acinar cells loaded with the fluorescent Ca2+ indicator fura-2. Both zero Mg2+ and an elevated [Mg2+]o significantly reduced the ACh-induced rise in the peak and the plateau phase of the Ca2+ transient that was seen in normal [Mg2+]o. In parotid acinar cells loaded with the fluorescent Mg2+ indicator magfura-2, ACh elicited a gradual decrease in intracellular free Mg2+ concentration ([Mg2+]i) to below the basal level. The results indicate that both hypo- and hypermagnesaemia may reduce both basal and ACh-evoked amylase secretion from the salivary gland. As far as the ACh-evoked response is concerned, the effect may be exerted by a decrease in cellular Ca2+ transport. Experimental Physiology (2002) 87.3, 321-326.

Type
Full Length Papers
Information
Experimental Physiology , Volume 87 , Issue 3 , May 2002 , pp. 321 - 326
Copyright
© The Physiological Society 2002

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