[The effect of proteinase inhibitors in rats. 1. Report. Effect of a short-term application on the N balance, the free amino acids in liver and muscles and the biological half-life of the intestinal tissue proteins].

Short-term trials with a triazin derivative and a peptide aldehyde were carried out to investigate the in-vivo administration of proteinase inhibitors in rats for improving the N balance of the animals. The results of N balances suggest that the peptide aldehyde may be regarded as a promising substance that may be used to increase the rate of utilization of the absorbed N in the intermediary metabolism. The short-term use of both active compounds did not affect the true N digestibility. The two compounds did not influence the concentration of free amino acids in the liver and muscle tissue under the experimental feeding conditions used. Similarly, tests of the biological half-life of proteins taken from the small and large intestine did not reveal any changes due to the presence of the inhibitors. Animals receiving a protein-free diet exhibited longer half-life periods for proteins from the small and large intestine compared with animals of the other groups. A protein-free nutrition of the animals caused a general increase in the levels of free non-essential amino acids in the liver. This was accompanied by a simultaneous decrease in essential amino acids. The same type of nutrition led to a general decline in the concentration of free amino acids in muscular tissue, particularly of the essential amino acids. High-protein nutrition led especially to an increase in the concentration of branched-chain amino acids in both types of tissues investigated.