Effect of magnesium on active and passive sodium transport in the human ileum.

The effect of 12.5 mM magnesium chloride on sodium transport in the human ileum in vivo was investigated using segmental perfusion. Choline chloride was used as a control. During perfusion of a balanced electrolyte solution containing isotopes of sodium and chloride, magnesium reduced unidirectional flux of sodium in both directions across the ileum; magnesium had no statistically significant effect on net sodium absorption, on chloride fluxes, or on potential difference. When sodium-free test solutions were infused, magnesium (and calcium) reduced net sodium secretion compared with choline and potassium. These results suggest that magnesium (and calcium) reduce passive sodium movement across ileal mucosa.