Metabolism of Glycine and Threonine in Growing Rats at Various Dietary Protein Levels(Food & Nutrition)

概要

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The metabolic fates of the carbon skeletons of [U-^<14>C]glycine and L-[U-^<14>C]threonine were investigated in growing rats fed with diets containing different percentages of protein calories (0, 5, 10, 15, and 30PC%) at 4100 kcal of metabolizable energy per kg of diet. The incorporation of ^<14>C into the body protein at 12 hr after the injection of ^<14>C-glycine was about 58% of the dose in rats fed with the 10 or 15 PC% diet, and the values were reduced in both the lower and higher PC% groups. A considerable amount of ^<14>C was recovered in the soluble fraction, and it was attributed to labeled glycine and serine in the free amino acid pools of the tissues. The incorporation of ^<14>C into the body protein from ^<14>C-threonine was extremely high in the dietary groups of 0 to 10 PC%, and it decreased in the 30 PC% group. Conversely, the expired ^<14>CO_2 production was much less until the dietary protein level reached at 10PC%, and it increased with higher PC% in the diets. The change in the activity of hepatic threonine dehydratase in rats fed diets with increasing protein levels was similar to that of the expired ^<14>CO_2 production from ^<14>C-threonine. These results indicate that, though the metabolic patterns for glycine and threonine differ from each other, their responses to dietary protein levels change at 10 to 15PC%, where the growth rate reached its approximate maximum.
社団法人日本農芸化学会の論文
1987-11-23