[Changes in protein metabolism in white rats with limited feeding and a varying physical load]

Changes in some protein metabolism indicators are studied in white rats at different levels of the energy balance. It is established that the level of the so-called labile protein in the organism is closely related to the level of energy metabolism and also, that it is not invariably directly dependent on protein concentration within the organism. The inference is reached that adaptivity of protein metabolism is manifested not merely through changes in the value of proteins, which might be employed in the capacity of reserve, but also through changes in the degree of their lability, resp. in the ability of the organism to mobilize them. The amount of protein reserves depends rather more on the increased protein intake with the while food, while the degree of reserve protein lability is related to a higher degree to the muscular activity of the organism. Restricted motor activity combined with a high protein intake, against the background of an even minimum hypercaloric feeding, leads to a considerable reduction of protein reserves. Deficient feeding combined with restricted motor activity leads to reduction both of the amount and lability of reserve proteins. Physical exertions have a favourable effect on the ability of organism both to increase its protein reserves and to mobilize them, with the latter being rather pronounced under conditions of limited feeding. It is stressed that excretion of nitrogen, urea and creatinine in the urine in conditions of protein poor diet is in a position to afford essential information on the adaptability of protein metabolism within the organism.