| [ Summary ] |
Magnesium is absorbed by the gastrointestinal tract and excreted via the kidney. The absorption pathways are divided into two types ; a paracellular and a transcellular pathways. In the transcellular pathway, the transient receptor potential melastatin 6 (TRPM6) functions as a Mg2+-permeable ion channel in the apical membrane. The expression of TRPM6 is affected by dietary magnesium concentration. Other suspected transporters such as Na+/Mg2+-exchanger may be involved in the transport of Mg2+ in the basolateral membrane. The paracellular pathway is important in leaky epithelia. Paracellular permeability for ions is regulated by claudins and occludin. Claudins consist of a family of at least 24 homologous isoforms. The expression pattern of each claudin is different in various tissues. In the kidney, claudin-16 forms divalent cationspermeable pore in the tight junction of the thick ascending limb of Henle, but it is not expressed in the intestine. Therefore, it is not known whether a specific claudin is involved in the transport of Mg2+ in the intestine. Chronic magnesium deficiency may be associated with various diseases such as diabetes, hypertension, and coronary heart disease. It is necessary to clarify the molecules involved in the absorption of Mg2+ in the intestine and the regulatory mechanisms of magnesium transporters. |