Total plasma clearance of intravenous essential amino acids: evidence of abnormal metabolism of amino acids in chronic renal failure.

The total plasma clearance of essential amino acids was studied in 9 non-dialyzed patients with stabile chronic renal failure and 20 healthy young adult volunteers after a bolus infusion of 0.28 g amino acids per kg of body weight in a solution containing essential L-amino acids in the proportions suggested by Rose and supplemented by L-histidine. After the infusion, the plasma concentrations of amino acids were observed for 6 hr. The pharmacokinetic analysis was performed by a polyexponential parameter estimate computer program, capable of analyzing up to five-compartment models. Wide individual variation in the capability to clear the given amino acid load from the plasma was observed. Expressed as a fraction of the sum of the total plasma clearances of the infused amino acids, the total plasma clearance of valine and phenylalanine had decreased in renal failure while that of histidine had increased. These alterations reflect the complex disorder of the protein metabolism and the observations may be of help in designing optimal nutritional regimens in renal failure.