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Interactions between magnesium and calcium in beta-cell-rich pancreatic islets
The American Journal of Physiology
|June 1, 1983
Summary
Magnesium ions (Mg2+) inhibit calcium (Ca2+) uptake and insulin release in pancreatic cells. Mg2+ also affects calcium transport, suggesting it plays a role in regulating cellular calcium levels.
Area of Science:
- Endocrinology
- Cell Physiology
- Mineral Metabolism
Background:
- Insulin release from pancreatic beta-cells is regulated by intracellular calcium (Ca2+) levels.
- Magnesium (Mg2+) is an essential cofactor for many enzymes and plays a role in cellular ion transport.
Purpose of the Study:
- To investigate the interactions between calcium and magnesium in pancreatic beta-cells.
- To determine the effect of Mg2+ on Ca2+ uptake, efflux, and insulin release.
Main Methods:
- Experiments were conducted using beta-cell-rich pancreatic islets isolated from ob/ob mice.
- Radioactive 45Ca was used to measure Ca2+ uptake and efflux.
- Insulin release was measured in response to glucose or high potassium concentrations.
Main Results:
- Mg2+ inhibited both 45Ca uptake and glucose- or high potassium-stimulated insulin release.
- Mg2+ influenced 45Ca efflux, reducing basal efflux and diminishing the effect of glucose when Mg2+ was added to depleted media.
- Ca2+ but not Mg2+ stimulated 45Ca efflux in a medium depleted of Ca2+, Mg2+, and Na+.
Conclusions:
- Mg2+ appears to interfere with Ca2+ entry through voltage-dependent Ca2+ channels.
- Mg2+ may also inhibit Ca2+ efflux via a mechanism distinct from Na+-Ca2+ countertransport.
- Intracellular Mg2+ levels are stable under physiological conditions, making significant fluctuations unlikely to be involved in Ca2+ regulation.