Kaysen G A, Carstensen A, Martin V I
Department of Medicine, Veteran's Administration Medical Center, Martinez, Calif.
Miner Electrolyte Metab. 1992;18(2-5):228-32.
Muscle protein synthesis is impaired in nephrotic rats: muscle and hepatic protein synthesis was measured as the incorporation of [3H]phenylalanine [3H]phe) into muscle and liver in male Sprague-Dawley rats with passive Heymann nephritis (HN) in comparison to both normal male (SDM) and female Sprague-Dawley rats (SDF). Incorporation of [3H]phe was significantly less muscle in HN (1.55 +/- 0.08 x 10(4) cpm/g muscle/h) than in SDM (2.55 +/- 0.14 x 10(4), p < 0.01) and no different than in SDF (1.64 +/- 0.23 x 10(4)). Growth rate was also significantly less in SDF and HN compared to SDM. Total [3H]phe incorporation and the % of [3H]phe incorporated into muscle correlated inversely with urinary albumin excretion in HN (p < 0.01) but not with serum albumin. In contrast, [3H]phe incorporation was increased in livers of HN (13.89 +/- 0.99 x 10(3) cpm/g rat/h) compared to either SDM (5.96 +/- 0.38 x 10(3), p < 0.01) or SDF (4.71 +/- 0.35 x 10(3), p < 0.01). Total liver mass, liver protein content, and the ratio of liver weight/body weight were all increased in HN. There were no differences in liver weight, liver protein content, or the ratio of liver weight/body weight between SDM and SDF. We have previously shown that decreased muscle protein accrual in HN cannot be overcome by increasing dietary protein intake. Hepatic protein synthesis and mass are increased in proteinuric rats while muscle protein synthesis is reduced. As a consequence growth rate and muscle protein accrual are diminished in nephrosis. The mechanism responsible for reduced muscle protein synthesis in the nephrotic syndrome is unknown.
通过测量雄性Sprague-Dawley大鼠被动型Heymann肾炎（HN）模型中[³H]苯丙氨酸（[³H]phe）掺入肌肉和肝脏的情况，来检测肌肉和肝脏蛋白质的合成，并与正常雄性Sprague-Dawley大鼠（SDM）和雌性Sprague-Dawley大鼠（SDF）进行比较。与SDM（2.55±0.14×10⁴ cpm/g肌肉/小时）相比，HN大鼠肌肉中[³H]phe的掺入量显著减少（1.55±0.08×10⁴ cpm/g肌肉/小时，p<0.01），且与SDF（1.64±0.23×10⁴）无差异。与SDM相比，SDF和HN的生长速率也显著降低。在HN中，总的[³H]phe掺入量以及掺入肌肉中的[³H]phe百分比与尿白蛋白排泄呈负相关（p<0.01），但与血清白蛋白无关。相反，与SDM（5.96±0.38×10³ cpm/g大鼠/小时）或SDF（4.71±0.35×10³ cpm/g大鼠/小时）相比，HN大鼠肝脏中[³H]phe的掺入量增加（13.89±0.99×10³ cpm/g大鼠/小时，p<0.01）。HN大鼠的肝脏总质量、肝脏蛋白质含量以及肝脏重量/体重比均增加。SDM和SDF之间的肝脏重量、肝脏蛋白质含量或肝脏重量/体重比没有差异。我们之前已经表明，增加饮食蛋白质摄入量并不能克服HN大鼠肌肉蛋白质积累的减少。蛋白尿大鼠的肝脏蛋白质合成和质量增加，而肌肉蛋白质合成减少。因此，肾病患者的生长速率和肌肉蛋白质积累会降低。肾病综合征中肌肉蛋白质合成减少的机制尚不清楚。
