Methods Patients. Eight clinically stable men at the Veterans Administration Medical Center, Portland, Oregon, who had been under-going maintenance hemodialysis for 53 months (range, 22 to 141) were studied. Mean age was 55 6 SD years. Neither the edema-free body weight nor the predialysis serum urea nitrogen differed on the two days of study, and the grand means of these values on both days were 79 25 kg and 88 22 mgJlOO ml, respectively. Causes of renal failure were chronic glomerulonephritis in four patients, chronic pyelonephritis in two patients, acute cortical necrosis in one patient, and unknown in one patient.

Procedure. Each patient was studied during two 300-mm hemodialyses. Patients were fasted from midnight before the study until the end of the hemodialysis treatment. During one hemodialysis, patients received an intravenous infusion of 800 ml of normal saline. During the other dialysis, patients received an infusion of 800 ml containing 39.5 g of crystalline free L-amino acids (400 ml of Aminosyn® 10%, Abbott Laboratories Hospital Products Division, North Chicago, Illinois) and 200 g of d-glucose (400 ml of 50% glucose). The latter infusate provided (g infused per dialysis): histidine, 1.20; isoleucine, 2.88; leucine, 3.76; lysine, 2.88 (infused as lysine acetate; the quantity refers to free L-lysine); methionine, 1.60: phenylala-nine, 1.76; threonine, 2.08, tryptophan, 0.64; valine, 3.20; tyrosine, 0.18; alanine, 5.12; arginine, 3.92; proline, 3.44; serine, 1.68; glycine, 5.12. The amino acid composition of the infusate was confirmed by amino acid analyses. For each patient, the order of administration of the two infusates was determined randomly, and each of the solutions was given to four of the patients as their first infusion. Infusion of each solution was begun at the exact onset of the dialysis procedure and was continued at a constant rate until the termination of the dialysis. The solutions were infused with an IVAC®(IVAC Corporation, La Jolla, California) pump into the drip chamber of the venous outflow tubing from the dialyzer. Immediately after the last blood collection, patients drank a solution containing Polycose®(Ross Laboratories, Division of Abbott Laboratories, Columbus, Ohio) and fruit juice to prevent reactive hypoglycemia.