Amino acids in urine and plasma of urolithiasis patients.

Urine and plasma amino acids in healthy males and patients with calcium stones, were analyzed for thirty-four amino acids. There was no difference in urinary excretion of thirty-two amino acids between the two groups. Plasma values of taurine, aspartic acid, hydroxyproline, glutamic acid, glycine, alanine, cystathionine, ornithine and lysine were significantly higher in controls than in stone formers. Of these amino acids, aspartic acid, glutamic acid, glycine, alanine and lysine are the main amino acids of matrix protein in renal stones. The levels of aspartic acid, glutamic acid, glycine, alanine and lysine in the serum of normal individuals were higher than those in plasma. On the basis of the findings, these amino acids may form soluble complexes with calcium and heparin in stone formers. It is also possible that some amino acids act as promoters or inhibitors in the pathogenesis of calcium oxalate stones.