Nam T J, Noguchi T, Naito H
Department of Agricultural Chemistry, Faculty of Agriculture, University of Tokyo, Japan.
Br J Nutr. 1991 Jan;65(1):37-46. doi: 10.1079/bjn19910064.
Urinary excretion of acid-soluble peptides (ASP) was measured in rats given streptozotocin or dexamethasone. Streptozotocin-induced diabetic rats excreted increased amounts of urinary nitrogen and ASP-form amino acids. The urinary ratio for N:ASP-form leucine plus valine, which has been shown to reflect the efficiency of dietary N utilization, increased in the diabetic rats, suggesting the impaired utilization of dietary N (and re-utilization of endogenous N). Dexamethasone administration to adrenalectomized rats caused increased excretion of urinary ASP-form leucine plus valine with a concomitant increase in N excretion. However, urinary ratio for N:ASP-form leucine plus valine did not change significantly. The results suggested that dexamethasone caused increased degradation of body proteins, but maintained the efficiency of dietary N utilization or re-utilization of endogenous N. Based on the present observations and the hypothesis proposed previously by the present authors (Noguchi et al. 1988) that urinary excretion of ASP-form leucine plus valine reflects the rate of whole-body protein degradation and the urinary ratio for N:ASP-form leucine plus valine represents N utilization, the origin of urinary N in streptozotocin-diabetic and dexamethasone-administered rats is discussed.
在给大鼠注射链脲佐菌素或地塞米松后，测定其尿中酸溶性肽（ASP）的排泄量。链脲佐菌素诱导的糖尿病大鼠尿中氮和ASP形式氨基酸的排泄量增加。已证明反映膳食氮利用效率的尿中氮与ASP形式亮氨酸加缬氨酸的比值在糖尿病大鼠中升高，这表明膳食氮（和内源性氮的再利用）利用受损。给肾上腺切除的大鼠注射地塞米松会导致尿中ASP形式亮氨酸加缬氨酸的排泄增加，同时氮排泄也增加。然而，尿中氮与ASP形式亮氨酸加缬氨酸的比值没有显著变化。结果表明，地塞米松导致机体蛋白质降解增加，但维持了膳食氮利用或内源性氮再利用的效率。基于目前的观察结果以及本作者之前提出的假设（Noguchi等人，1988年），即ASP形式亮氨酸加缬氨酸的尿排泄反映全身蛋白质降解速率，而尿中氮与ASP形式亮氨酸加缬氨酸的比值代表氮利用情况，本文讨论了链脲佐菌素诱导糖尿病大鼠和注射地塞米松大鼠尿氮的来源。
