title: Contributions of individual body tissues to nitrogen excretion in adult rats fed protein-deficient diets.
abstract: An attempt was made to estimate the contributions of various tissues to nitrogen (N) excretion in rats fed protein-free diet or 2 and 10% lactalbumin diets for 14 to 31 days. The contributions were calculated as differences between the amounts of dietary N utilized for tissue protein and tissue growth. The amount of dietary N utilized for tissue protein was calculated from the recovery of 15N of orally administered [15N]leucine and N intake. The following results were obtained. 1) With a 10% protein diet, the contribution of tissues to N excretion was affected more by the turnover rates of individual tissues than by the size of the tissues, but with a protein-free diet the contribution was greatly affected by the size of the tissues. 2) With 2% lactalbumin diet, the contributions were not intermediate between those with protein-free diet and 10% lactalbumin diet: urinary N excretion was similar to that with protein-free diet in spite of the difference in N intake, probably mainly because the contribution of skeletal muscle was lower. 3) Differences in the dietary protein level affected the utilization of dietary protein only a little, but influenced body protein metabolism very much.
mesh_terms: D000818:Animals; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D005243:Feces / Q000032:analysis; D006197:Hair / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D011488:Protein Deficiency / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D004044:Dietary Proteins; D011506:Proteins; D009584:Nitrogen