Magnesium

Endpoint summary

Description of key information

Magnesium is an essential intracellular cation. Nearly 99% of the total body magnesium is located in bone or the intracellular space. Magnesium is a critical cation and cofactor in numerous intracellular processes. It is a cofactor for adenosine triphosphate; an important membrane stabilizing agent; required for the structural integrity of numerous intracellular proteins and nucleic acids; a substrate or cofactor for the activity of over 300 enzymes; a regulator of ion channels; an important intracellular signaling molecule; and a modulator of oxidative phosphorylation.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - dermal (%):

1

Additional information

Magnesium is absorbed in the intestinal tract. Urine is the major route of excretion under normal conditions. Magnesium is mainly distributed in bone and muscle, but some magnesium is present in every cell of the body. Tissue distributions indicate that of 20 g body burden. Magnesium is filtered by the glomeruli and reabsorbed by renal tubules.

Mechanism of Action:

Magnesium is a cofactor of many enzymes involved in intermediary metabolism. In the glycolytic cycle converting glucose to pyruvate, there are 7 key enzymes that require Mg2+. It is also involved in the citric acid cycle and in the beta oxidation of fatty acids.

Magnesium helps regulate blood sugar levels, promotes normal blood pressure, and is known to be involved in energy metabolism and protein synthesis .

 

A QSAR model predicts that the permeability of Magnesium to human skin is quite low. The permeability coefficient was determined to be 0.133 mg/cm2, which is around 1% of the skin penetration rate. Predicted dermally absorbed coefficient was determined to be Kp (est)=0.000465 cm/hr.

  Toxicokinetics, Metabolism and Distribution

Magnesium is a cofactor of many enzymes involved in intermediary metabolism. In the glycolytic cycle converting glucose to pyruvate, there are seven key enzymes that require Mg²⁺. It is also involved in the citric acid cycle and in the beta oxidation of fatty acids. Magnesium salts are poorly absorbed from the intestine. In cases of overload, this may be due in part to their dehydrating action. Magnesium is absorbed mainly in the small intestine; the colon also absorbs some.

Calcium and magnesium are competitive with respect to their absorptive sites, and excess calcium may partially inhibit the absorption of magnesium. Magnesium is excreted into the digestive tract by bile and pancreatic and intestinal juices. A small amount of radiomagnesium given intravenously appears in the gastrointestinal tract. The serum levels are remarkably constant. There is an apparent obligatory urinary loss of magnesium, which amounts to about 12 mg/day and the urine is the major route of excretion under normal conditions.Unabsorbed magnesium is excreted in the feces.Magnesium is filtered by the glomeruli and reabsorbed by renal tubules. In the blood plasma, about 65 percent is the ionic form while the remainder is bound to protein. The former is that which appears in the glomerular filterate. Excretion also occurs in the sweat and milk. As in the case of other essential elements, physiologic homeostatic mechanisms prevent large fluctuations in blood through changes in absorption and excretion.

Approximately 70 percent of serum magnesium is ultrafilterable, and about 95 percent of filtered magnesium is reabsorbed, an important factor in maintaining magnesium homeostasis. Endocrine activity-particularly of the adrenocortical hormones, aldosterone, and parathyroid hormone-also has an effect on magnesium levels, although this may be related to the interaction of calcium and magnesium.

Tissue distributions studies indicate that of 20 g body burden, the majority is intracellular in the bone and muscle including the myocardium, but some magnesium is present in every cell of the body.

Conclusion

Magnesium is absorbed in the intestinal tract and the urine is the major route of excretion under normal conditions. Magnesium is mainly distributed in the bone and muscle, but some magnesium is present in every cell of the body. Tissue distributions indicate that of 20 g body burden. Magnesium is filtered by the glomeruli and reabsorbed by renal tubules.