Ballmer P E, McNurlan M A, Milne E, Heys S D, Buchan V, Calder A G, Garlick P J
Rowett Research Institute, Aberdeen, United Kingdom.
Am J Physiol. 1990 Dec;259(6 Pt 1):E797-803. doi: 10.1152/ajpendo.1990.259.6.E797.
A new method for measuring albumin synthesis in humans with stable isotopes is presented. This can readily be applied in most clinical conditions, even when albumin losses are occurring or when repeated assessment is required. After rapid intravenous injection of a large dose of [13C]leucine (57 mg/kg body wt, 19.4 atoms%), plasma samples were taken at intervals up to 90 min. The enrichment of free leucine in plasma measured by gas chromatography-mass spectrometry rose to a peak at 10 min and then fell slowly, whereas that in liver biopsies (from surgical patients) ranged from 101.5 to 80.5% of the plasma value between 10 and 90 min after injection. The fractional synthesis rate (FSR) was calculated by dividing the increase in enrichment of leucine in albumin, measured by gas isotope ratio mass spectrometry, by the area under the plasma free leucine enrichment vs. time curve after allowing for the period between synthesis of the protein and its secretion into the plasma. The FSR in healthy postabsorptive males was 7.2 +/- 1.3%/day, and the absolute synthesis rate was 157 +/- 39 mg.kg body wt-1.day-1. These rates are comparable to those obtained by other methods.
本文介绍了一种用稳定同位素测量人体白蛋白合成的新方法。即使在白蛋白流失或需要重复评估的情况下，该方法也能很容易地应用于大多数临床情况。快速静脉注射大剂量的[¹³C]亮氨酸（57毫克/千克体重，19.4原子%）后，每隔一定时间采集血浆样本，最长至90分钟。通过气相色谱 - 质谱法测量的血浆中游离亮氨酸的丰度在10分钟时升至峰值，然后缓慢下降，而肝活检样本（来自手术患者）中的丰度在注射后10至90分钟内为血浆值的101.5%至80.5%。通过气相同位素比质谱法测量白蛋白中亮氨酸丰度的增加量，并在考虑蛋白质合成与分泌到血浆之间的时间间隔后，除以血浆游离亮氨酸丰度与时间曲线下的面积，计算出分数合成率（FSR）。健康空腹男性的FSR为7.2±1.3%/天，绝对合成率为157±39毫克·千克体重⁻¹·天⁻¹。这些速率与通过其他方法获得的速率相当。
