title: [Investigations of the connection between the quality of protein, the protein level and endogenous N-excretion].
abstract: The influence of various protein qualities as well as of different levels of protein on the amount of endogenous N-excretion, metabolic fecal nitrogen (MFN) and endogenous urinary N (EUN) was determined at growing albino rats. The test rations were labelled with admixtures of 15N-DL-methionine resp. 15N-DL-lysine or contained feed protein enriched with 15N. EUN and MFN and their sum (the N maintenance requirement) showed the influence of the respective protein source and its dependence on the protein level. The endogenous N-excretions showed an opposite tendency to the N-balance; for high-quality protein feedstuffs with a high N-balance (e.g. dried eggs) they are lower than for protein source of inferior quality, with a low N-balance only (e.g. wheat gluten). Presumably this interaction of retention and maintenance is due to the complementary effect of exogenous and endogenous amino acids in the N-resp. amino acid-pool. Provided that the N-dose and the liver weight of the animals are comparable, the N-balance appears to be more suitable as parameter for the description of the protein quality and the calculation of the protein utilisation than N-retention, as the sum of N-balance and the values of MFN and EUN (depending on the feedstuffs and the N-level).
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D005243:Feces / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats / Q000652:urine*; D012119:Respiration
chemical_list: D000596:Amino Acids; D011506:Proteins; D009584:Nitrogen
vernacular_title: Untersuchungen zum Zusammenhang zwischen Proteinqualität, Höhe der Proteingabe und endogener N-Ausscheidung.