Quan Z Y, Walser M
Department of Pharmacology and Molecular Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD 21205.
Metabolism. 1991 Dec;40(12):1263-7. doi: 10.1016/0026-0495(91)90026-s.
Adrenalectomized rats were implanted with pellets containing corticosterone in proportions varying from 0% to 100%, plus cholesterol. Stable levels of plasma corticosterone resulted, varying from close to zero (I) to physiologic (II) to supraphysiologic (III). Whole body protein synthesis (S) was measured during fasting by a technique involving injection of [1-14C]-leucine, analysis of expired air for 14CO2, and measurement of urinary excretion of urea N plus ammonia N (C). Whole body breakdown (B) during fasting was calculated as the sum of S and C. C rose progressively from I to III, but fractional oxidation of 14C leucine was lowest in II. Both S and B were markedly reduced in I and maximal in II. In III, S fell but B remained high. Thus variations in glucocorticoid levels above and below physiologic exert profound effects on leucine oxidation and protein turnover, involving effects on both synthesis and breakdown.
对肾上腺切除的大鼠植入含有皮质酮的小球，皮质酮的比例从0%到100%不等，再加上胆固醇。由此产生了稳定的血浆皮质酮水平，范围从接近零（I）到生理水平（II）再到超生理水平（III）。在禁食期间，通过一种技术测量全身蛋白质合成（S），该技术包括注射[1-14C]-亮氨酸、分析呼出气体中的14CO2以及测量尿素氮加氨氮的尿排泄量（C）。禁食期间的全身分解代谢（B）计算为S和C之和。C从I到III逐渐升高，但14C亮氨酸的氧化分数在II中最低。S和B在I中均显著降低，在II中最高。在III中，S下降但B仍然很高。因此，糖皮质激素水平在生理水平上下的变化对亮氨酸氧化和蛋白质周转有深远影响，涉及对合成和分解的影响。
