Aminoaciduria in chronic renal failure--its relationship to vitamin D and parathyroid status

Fractional clearances of amino acids in 24 patients with chronic renal failure indicate that aminoaciduria is common and often severe. Eleven studies have also been carried out in ten patients with stable renal failure before and during treatment with different metabolites of vitamin D. Sequential measurements of fractional clearance of amino acids, plasma 25-hydroxy-vitamin D (25-(OH)D) and serum parathyroid hormone were made. All patients initially had hyperaminoaciduria, secondary hyperparathyroidism and osteomalacia. Treatment with 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) or 1 alpha-hydroxycholecalciferol (1 alpha(OH)D3) significantly improved amino acid reabsorption irrespective of the initial degree of aminoaciduria. Cholecalciferol or 25-hydroxycholecalciferol(25(OH)D3) improved amino acid transport in patients with initially mild hyperaminoaciduria, but not in patients with severe hyperaminoaciduria. Reduction in aminoaciduria during treatment with 25(OH)D3 may have depended on a variable ability to synthesize 1,25(OH)2D3. Changes in amino acid transport did not correlate with changes in serum parathyroid hormone. It is suggested that defective amino acid reabsorption in patients with chronic renal failure is due at least in part to deficiency of 1,25(OH)2D3.