Age dependence of the utilization of different quality proteins in animal experiments.
Male rats aged 45, 85, 145 and 270 days (daily body mass increments on an optimal diet containing casein were 6.73, 2.88, 0.53 and 0.31 g respectively) were fed 15 days ad libitum on a diet with a nutrient content physiological for their age, in which the protein source was milk casein (ratio of essential to nonessential amino acids E/N = 0.79, compensation coefficient K = 14) or wheat gluten (E/N = 0.30, K = -8). In the case of gluten, net protein utilization (NPU) fell markedly in rapidly growing animals aged 45 and 85 days (33 and 30% more than with casein), indicating that without essential amino acid compensation, gluten is inadequate for animals of this age, whose organism requires fully ensured proteosynthesis for growth and development. In adolescence and adulthood (145 and 270 days), the utilization of proteins is not dependent on their quality (the decrease in NPU 13 and 12%--is nonsignificant). That means that a smaller amount of essential amino acids, including the limiting amino acid in uncompensated protein, is sufficient for the maintenance and renewal of organs and tissues, i.e. for proteosynthesis. The activation of gluconeogenesis (phosphoenolpyruvate carboxykinase activity in the liver) after the intake of plant protein confirms the effect of proteins on catabolic processes.
Krajcovicová-Kudlácková
M
M
Research Institute of Nutrition, Bratislava.
D000375:Aging / Q000502:physiology*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D015992:Body Mass Index; D002364:Caseins / Q000737:chemistry / Q000378:metabolism; D005983:Glutens / Q000737:chemistry / Q000378:metabolism; D006128:Growth / Q000187:drug effects; D008297:Male; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000096:biosynthesis; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D000596:Amino Acids; D002364:Caseins; D011506:Proteins; D005983:Glutens; D010729:Phosphoenolpyruvate Carboxykinase (GTP)