Effect of Different Essential Amino Acid Deficiencies on Amino Acid Pools in Rats

The effects of single essential amino acid deficiencies on the quantities of free amino acids present in plasma, liver, and muscle were investigated. Rats were force-fed for 3-day periods diets devoid in either leucine, isoleucine, valine, or threonine. At 8 hours postprandial, the amino acid limiting in the diet, without exception, was decreased in concentration in plasma and liver tissue. However, leucine and threonine showed greater decreases in concentration in the amino acid pools when these amino acids were omitted from the diet than the decreases for isoleucine or valine when these amino acids were deficient. The changes in amino acid concentrations in liver tissue were correlated with those in plasma to a greater extent than the alterations in amino acid values of muscle tissue. When rats were fed the diet without leucine, significant elevations occurred in many of the amino acids in the amino acid pools and, particularly in isoleucine and valine.