Uezu N, Yamamoto S, Rikimaru T, Kishi K, Inoue G
J Nutr. 1983 Jan;113(1):105-14. doi: 10.1093/jn/113.1.105.
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.
研究人员试图估算在给大鼠喂食无蛋白饮食、2%和10%乳白蛋白饮食14至31天后，各种组织对氮（N）排泄的贡献。这些贡献是通过用于组织蛋白和组织生长的膳食氮量之间的差异来计算的。用于组织蛋白的膳食氮量是根据口服[15N]亮氨酸的15N回收率和氮摄入量计算得出的。得到了以下结果。1）在10%蛋白质饮食条件下，组织对氮排泄的贡献受单个组织周转率的影响大于受组织大小的影响，但在无蛋白饮食条件下，贡献受组织大小的影响很大。2）在2%乳白蛋白饮食条件下，其贡献并非介于无蛋白饮食和10%乳白蛋白饮食之间：尽管氮摄入量不同，但尿氮排泄与无蛋白饮食时相似，这可能主要是因为骨骼肌的贡献较低。3）膳食蛋白质水平的差异对膳食蛋白质的利用影响很小，但对机体蛋白质代谢影响很大。
