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Characterization of a sodium‐dependent magnesium efflux from magnesium‐loaded rat pancreatic acinar cells
Author(s) -
Wisdom DM,
Geada MM,
Singh J
Publication year - 1996
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1996.sp003941
Subject(s) - efflux , chemistry , magnesium , bumetanide , amiloride , sodium , quinidine , extracellular , ion transporter , antiporter , potassium , cotransporter , ouabain , choline , biophysics , medicine , endocrinology , biochemistry , membrane , biology , organic chemistry
This study investigates the mechanism of magnesium (Mg2+) transport (efflux) from the exocrine rat pancreas. Permeabilized pancreatic acini were loaded with Mg2+ by employing a high‐Mg2+ (12 mM) buffer containing A23187 (6 microM). Net Mg2+ efflux was measured using the technique of atomic absorbance spectrophotometry. Incubation of preloaded acini in a buffer deficient in Mg2+ resulted in a large and time‐dependent release of Mg2+ with maximal efflux occurring within 40 min. Pretreatment of loaded acini with bumetanide, SITS or ouabain had no significant effect on Mg2+ efflux. In contrast, when acini were pretreated with 10 mM dinitrophenol, 10(‐4) M amiloride, 1 mM lidocaine or 1 mM quinidine there were significant (P < 0.001) decreases in net Mg2+ efflux. Replacement of extracellular sodium [Na+]o with either N‐methyl‐D‐glucamine (NMDG), Tris or choline resulted in a significant (P < 0.001) inhibition of Mg2+ efflux. The results of this study indicate that Mg2+ transport (efflux) in pancreatic acinar cells may not be associated with the Na(+)‐K(+)‐ATPase, the Na(+)‐K(+)‐Cl‐ cotransporter or the anion exchanger, but with a Na(2+)‐sensitive Mg2+ transport system.