The Effects of Test Doses of Leucine, Isoleucine or Valine on Plasma Amino Acid Levels

Abstract

Test doses of 2 gm. of leucine, isoleucine or valine were administered orally to fasting obese and normal weight subjects; plasma amino acid levels were determined at intervals during a 4 hour period. In all subjects, characteristic plasma clearances were obtained with each of the branched chain amino acids. The fasting level of leucine was re-established after 4 hours, but the isoleucine and valine levels were still elevated with valine showing the greatest increase over the fasting value. Of the amino acids administered, only leucine reduced the plasma levels of the other branched chain amino acids. A 10 gm. test dose of leucine accentuated this reduction and other essential amino acids were also decreased. No clear-cut differences could be demonstrated in the response of obese and normal weight subjects to the administration of the branched chain amino acids.