Abstract
Experiments were conducted to determine the influence of gastrointestinal microflora on nitrogen metabolism in rats, by analyzing the nitrogen and amino acid content of urine from germfree (GF) and conventional (CV) rats fed an 18% casein diet and a protein-free diet. During the casein diet period, significantly greater amounts of nitrogen, urea-N, allantoin and 3-methylhistidine were excreted into the urine, and the ratio of urea-N to urinary nitrogen was greater in the CV group than in the GF group. Total urinary and free amino acid excretions showed significantly opposite trends. During the protein-free diet period, urinary ammonia-N, creatinine, allantoin and 3-methylhistidine were excreted in significantly greater amounts in the CV group than in the GF group. However, urinary nitrogen, urea-N and total amino acids were essentially the same in the two groups, although free amino acid excretion in the GF group far exceeded that in the CV group. Both groups showed essentially the same plasma amino acid concentration. These results suggest that gastrointestinal microflora may accelerate urea synthesis and body protein breakdown in the host.
