[Determination of data of protein metabolism kinetics from studies with 15N labeled feed].

The protein metabolism of normal growing rats was investigated in studies with 15N labelled feeding-stuffs (spring barley and feed yeast) which were based on a model developed by CZARNETZKI and coworkers (1969). Data on the kinetics of protein metabolism were calculated from the balances between the quantities of nitrogen and 15N ingested and those excreted with the faeces and urine. The rate of synthesis for the body proteins of growing rats (100 g liveweight) was found to be dependent upon the protein intake. 0.84 g of body protein were synthesized per day when 100 mg N were ingested. This rate increased to 1.8 g per day when the intake was 400 mg N. The rate of protein decomposition was also shown to be dependent on the level of protein consumption. The mean period of nitrogen retention in body proteins was shown to be about 30 days, the nitrogen pool was determined to be 0.30 g N.