Methods

Thirty-five healthy males and 3 healthy females between the ages of 19 and 27 years served as subjects for this study. The objectives of the study, the nature of the test materials, and their expected effect upon the test subject were explained to each participant. Fully informed consent for the performance of the tests was thus given by all subjects. Each subject continued his usual diet but took no food for at least 8 hours before testing. A subject was tested with as many of the test materials as possible, and, when feasible, repetitive testing with the same amino acid solutions was performed. In-dividual amino acids and mixtures of 2 to 10 amino acids were administered intravenously in amounts of from 2.5 to 30 g. The composition of the mixture of 10 essential amino acids and of mixtures of 6 to 8 amino acids (solutions A through G), administered in 30-g amounts, is given in Table I. Other mixtures were made up of 2, 3, 4, 5, or 8 amino acids in the same amounts in which they had been present in the 30 g of the mixture of 10 amino acids.

During or after the infusion of some individual amino acids a few subjects experienced untoward reactions, the details of which are given in the Results. When reac-tions occurred, further testing at or beyond that dose level was not performed and is not recommended. Essential I-amino acids 2 were obtained in crystalline form as the pure amino acids except for lysine, which was the hydrochloride. In some instances histidine and arginine also were obtained as the hydrochloride. Aque-ous amino acid solutions were prepared in concentrations