[Nitrogen retention in germ-free and conventional mice reared on an antigen-free diet and the significance of the appearance of protein nitrogen in their feces].

: The nutritional state of animals removed from as much antigenic stimuli as possible--germ-free mice on an antigen-free liquid diet--was compared with that of conventional mice through assessment of their protein metabolism. Both the germ-free and conventional mice reared on the antigen-free liquid diet for 7 weeks exhibited relatively stable body weight throughout the experimental period. Although the nitrogen retention rate was generally higher for the conventional mice, even in the germ-free mice with the exception of one observation in a male, positive nitrogen retention rates were observed, and this suggests nutritional adequacy of the diet. The amount of protein-nitrogen excreted in the feces due to the physiological processes, such as the digestive tract cell turnover, digestive juice secretions, etc, (4.2-5.3 mg/mouse/week), and the amount that was influenced by the presence of intestinal bacteria and due to bacterial protein per se (2.3-4. 4 mg /mouse/week) could be estimated through the comparison of the fecal protein values obtained from germ-free and conventional mice reared on the antigen-free liquid diet.