[The effect of high fat intake in rats of different age categories on protein utilization].

Male rats of the Wistar strain, age 30, 75, 90 and 150 days, were given high-fat feeds (45%, 36.5%, 33% and 30%) ad libitum for 14 days. The net protein ratio (NPR), net protein utilization (NPU), and liver protein utilization (LPU) of the biological value of proteins were determined in comparison with diets considered as optimum for each age category. The specific activity of phosphoenol-pyruvate carboxykinase PEPCK (E.C..4.1.1.32) was measured in the liver of the animals. As demonstrated by the significantly reduced parameters of the biological value of proteins and the activated process of gluconeogenesis, a high intake of fats adversely affected the utilization of proteins in the organisms of 75 to 90 days old animals. The decrease in the NPR and NPU of the weanlings is insignificant; the increase in PEPCK is at the level of significance, which testifies to a good tolerance to the intake of fats by the animals after weaning, with respect to a similar composition of mothers' milk. In the animals with the slower growth and higher protein requirement for the maintenance of the organism (150 days old rats) the reduction of protein utilization and the increase in PEPCK activity as a result of a high fat intake are not so significant as in animals old 75 and 90 days. As suggested by the results, it is necessary to state another length of high-fat administration than 14 days.