LEUCINE TRNOVR RATS W/ NEPHROTIC SYNDROME SUGGEST BODY PROTEIN CONSERVATION

对8例慢性阻塞性肺疾病患者的全身亮氨酸流量进行了测定。 肾病综合征及5例正常受试者的预置常数 静脉滴注L-[L-13C]亮氨酸。~(13)C的血浆浓缩 用气相色谱/质量法测定亮氨酸和13CKIC 用同位素比值质谱仪测定13CO2的呼出量。 亮氨酸流量的所有参数，包括亮氨酸率 氧化，蛋白质降解释放亮氨酸，到较低水平 程度，亮氨酸掺入蛋白质，减少在 肾病患者。的值(平均值(SD，umol/kg/hr) 肾病患者和对照组的不同参数分别为 来自蛋白质降解的亮氨酸，99(6和117(12(p=0.007)； 亮氨酸氧化率15(7和22(3，(p=0.04))亮氨酸氧化率 加入全身蛋白质，8484+10和95+6，(p=0.04)，以及 净亮氨酸平衡，即 蛋白质合成和降解分别为-15+7和-22+3(p=0.04)。这是 E负值是由于进行了测量的事实 禁食12小时后。蛋白质周转率，由亮氨酸计算 肾小球滤过率分别为3.9±0.4g/kg/d和4.7±0.3g/kg/d。 对照组(P=0.007)。氮平衡，仅以 肾病患者的平均正平衡为0.5g/d。为 在研究的前几天，患者摄入了由以下组成的控制饮食 蛋白质0.84g/kg/d和33.3(9Kcal/kg/d)。因此，在这个层面上， 蛋白质/能量摄入，肾病患者维持氮平衡 也许是因为一种新陈代谢适应导致了 蛋白质降解和氨基酸氧化速率的调节。

Whole body leucine flux was measured in eight patients with nephrotic syndrome and in five normal subjects by primed-constant intravenous infusion of L-[l-13C]leucine. Plasma enrichment of 13C leucine and 13CKIC were measured by gas chromatography/mass spectrometry and exhaled 13CO2 by isotope ratio mass spectrometry. All parameters of leucine flux, including the rates of leucine oxidation, leucine release from protein degradation and, to a lesser extent, leucine incorporation into protein, were reduced in the nephrotic patients. The values (means (SD, umol/kg/hr) of the different parameters in the nephrotic patients and the controls were Leucine derived from protein degradation, 99(6 and 117(12 (p=0.007); leucine oxidation rate 15(7 and 22(3, (p=0.04) the rate of leucine incorporationinto whole body protein, 8484+10 and 95+6, (p=0.04), and net leucine balance which is the difference between the rates of protein synthesis and degradation was -15+7 and -22+3, (p=0 .04). Th e negative values are due to the fact that measurements were made after a 12 hr fast. Protein turnover rate, calculated from leucine flux, were 3.9+0.4 and 4.7+0.3 g/kg/day in the nephrotic and the control grops (p=0.007). Nitrogen balance, measured only in the nephrotic patients, showed a mean positive balance of 0.5 g/day. For days prior to study the patients ingested a controlled diet consisting of 0.84 g protein/kg/d and 33.3(9 Kcal/kg/day. Thus, at this level of protein/energy intake, nephrotic patients maintained nitrogen balance perhaps because of a metabolic adaptation that resulted in a down regulation of protein degradation and amino acid oxidation rates.