The goal of this project is to evaluate the clinical and biochemical consequences of nitrogen reutilization, by means of feeding alpha-keto analogues of essential amino acids, microencapsulated urease, and an almost nitrogen-free diet. Under these circumstances the keto acids may be converted to the corresponding amino acids by amination or transamination; ammonia derived from accelerated ureolysis in the gut may provide non-essential nitrogen. Plasma urea level and urea excretion may fall to very low levels. Thus it may be possible to obtain nearly normal rates of protein synthesis in the near absence of dietary nitrogen. This maneuver may prove to be helpful in acute or chronic renal failure, and in patients with gastrointestinal disorders who cannot assimilate protein. The keto acids will be synthesized and their purity and identity established. Animal studies of possible toxicity and efficiency of conversion to amino acids will be performed. Patients with chronic renal failure will be given these drugs while on a protein-free diet. Free amino acid pools, nitrogen excretion, and the fate of N15 from labelled urea will be measured to evaluate the results.