Effect of 1,25-(OH)₂D₃ on jejunal absorption of magnesium in patients with chronic renal disease

These studies were performed to see if jejunal malabsorption of magnesium in patients with chronic renal disease was influenced by therapy with 1α,25-dihydroxyvitamin D₃ [1,25-(OH)₂D₃; 2 μg/day by mouth for 7 days]. This treatment restored normal serum concentrations of the vitamin D metabolite from 0.9 ± 0.2 to 4.2 ± 0.6 ng/dl. Jejunal absorption of magnesium, measured by a triple-lumen constant-perfusion technique, was enhanced in each of the seven patients by this therapy. The mean value rose from 0.04 ± 0.02 to 0.13 ± 0.02 mmol.30 cm^-1.h^-1. This last value is similar to the magnesium absorption rate in untreated normal subjects. These results demonstrate that magnesium absorption in the human jejunum is dependent on vitamin D, and they show that 1α,25-dihydroxyvitamin D₃ therapy in patients with chronic renal failure is associated with an enhanced jejunal absorption of magnesium.