Blood Amino Acid Studies: Ii. Effects of Dietary Lysine Concentration, Sex, and Growth Rate on Plasma Free Lysine and Threonine Levels in the Rat

Abstract

Plasma free lysine levels of growing female rats given a lysine-deficient diet supplemented with graded amounts of lysine were higher than those of males. In both sexes, plasma free lysine values rose rapidly in response to added dietary lysine, and reached a maximum at a dietary lysine concentration of approximately 1.0%. This amount of dietary lysine was about 0.2% greater than that found necessary for maximum growth. Male rats given diets containing rapeseed oil and graded amounts of lysine showed reduced growth and lower plasma lysine and threonine levels as compared to animals given similar diets containing corn oil, but the amount of dietary lysine required for maximum plasma lysine levels was not influenced by the growth rate. Plasma free threonine levels showed a reciprocal relationship with those for lysine. It was concluded that measurement of the ratio between plasma free lysine and threonine levels may provide a sensitive indication of the adequacy of the dietary lysine content.

Whole-body protein metabolism and plasma profiles of amino acids and hormones in growing barrows fed diets adequate or deficient in lysine

“…The alteration in the plasma amino acid profile observed in this experiment due to the transition from deficiency to adequate lysine supply is in agreement with results reported by others for various amino acids (Morrison et al 1961;Zimmerman and Scott 1965;Brookes et al 1972). The increment of lysine concentration between the lysine-supplemented diets (L2 and L3) and the lysine-deficient diet (L1) was expected because, at low dietary lysine concentra- tions, lysine will be retained intracellularly for preferential channeling into PS rather than to oxidation or to release to the blood circulation.…”

Effects of cyclophosphamide and diets on sister chromatid exchange frequency of rats.

“…If a diet is low in a specific amino acid, other amino acids present in the diet are not as completely utilized. This specific amino acid is considered to be a limiting amino acid in the diet (Morrison et al 1961). Knowledge of limiting amino acids is important: supplementation of proper amino acids to a diet increases the nutritional value of the diet as well as the growth rate of the subject; supplemen tation to diet with improper amino acids will be a waste and may result in amino acid imbalance.…”

“…This specific amino acid is then a limiting amino acid in this diet (Morrison et al 1961). In this research, the fasting plasma profile equivalent (FPPE) concept Pytelewski 1975, Dubroff et al 1979) was used to determine the order of limiting amino acids.…”

Metabolism of Lysine, Threonine, and Leucine in Growing Rats on Gluten or Zein Diets at Various Dietary Protein Levels

“…These phenomena have been recognized by several workers. 26 -30) Gray et al 28 ) and Morrison et al 29 ) reported that the chicks given a lysine-deficient diet had lower levels of free lysine and higher levels of free threonine in the plasma than those given a diet containing adequate amounts of lysine.…”