Changes in the urinary excretion of acid-soluble peptides in rats injected with streptozotocin or dexamethasone: a trial to estimate the changes in the rate of whole-body protein degradation in those rats

Abstract

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 (Noguchiet 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