Untersuchungen zur Wirkung von Proteinaseinhibitoren bei Ratten

Abstract

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.

Estimation of rate of protein synthesis by constant infusion of labelled amino acids in pigs

“…In earlier experiments with rats we found values for the half-life for protein breakdown in the small and large intestine of 1.6 and 2.6 d respectively (Simon, Bohley, Huckel, Munchmeyer & Bergner, 1976).…”

“…Some investigators suggest that amino acids from an extracellular precursor pool may move directly into the synthetic machinery (Kipnis, Reiss & Helmreich, 1961;London, I 972;Venrocij, Poort, Kramer & Jansen, 1972). However, other investigators have concluded that the intracellular pool or some portion of it, represents the true source of amino acids (Tsukada, Moriyama & Lieberman, 1971 ;Alpers & Thier, 1972;Fern & Garlick, 1973Li, Fulks & Goldberg, 1973). Airhart et af.…”

“…Consequently the specific activities of the free amino acids in either plasma or tissues have been used. Because of the rapid change in the specific activity of an amino acid after a single injection of label (Henriques, Henriques & Neuberger, I 955 ; Simon, Miinchmeyer, Bergner & Zebrowska, 1976) a method was employed in which a plateau in the specific activity of free amino acids in plasma and tissue was reached using a continuous infusion of labelled amino acids (Waterlow & Stephen, 1967, 1968Garlick, 1969). A single measurement of the specific activity of protein-bound and free amino acids at the end of 6 h infusion was used to calculate the rate of protein synthesis (Garlick, Millward & James, 1973).…”

Inhibition of cysteine proteinases in lysosomes and whole cells

“…Leupeptin, an inhibitor of both serine and cysteine proteinases, inhibits basal protein turnover by 30-40 % (Dean, 1979). Initial experiments looking at the inhibitory characteristics of this compound seemed to indicate that it rapidly entered cells by diffusion, since its effect was observed without any discernible lag time (Simon et al, 1977;Seglen et al, 1979). In conflict with these results, Nonaka and colleagues (1982) administered [14C]leupeptin orally to dystrophic chickens and looked at the distribution of [14C]leupeptin.…”