Stable isotope 15N-urea and clinical research in nephrology

Stable isotope 15N-compound, 15N-urea, is useful marker to investigate nitrogen metabolism in clinical nephrology, particularly in chronic renal failure or dialysis. 15N-urea incorporation into plasma albumin in addition to plasma 15N disappearance was studied in 6 patients with endstage chronic renal failure. As a result, only minor fraction of administered 15N-urea was incorporated into albumin in this study. In addition, it was also confirmed that high energy diet may promote protein synthesis through 15N incorporation to plasma amino acids, such as alanine, in these patients with low protein meal. Therefore, administration of 15N-compound to human subjects may contribute to provide us the important informations on nitrogen metabolism. For instance, urea kinetics are described in the endstage chronic renal failure in this review. However, less expensive 15N-compounds should be provided and more simple but accurate measurement of 15N activity should be developed for the further clinical application of the stable isotope.