Agarwal Rajiv
Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
Am J Physiol Renal Physiol. 2005 Feb;288(2):F265-71. doi: 10.1152/ajprenal.00318.2004. Epub 2004 Oct 5.
Albuminuria is an excellent marker of cardiovascular and renal prognosis. Commercially available tests of immunodetectable albumin in the urine may not identify posttranslationally modified albumin that makes it undetectable to antibodies. Also, it is unclear whether albumin is degraded to smaller fragments, such as through proteolysis, in the course of acute renal injury. In 20 men with chronic kidney disease, we measured excretion rates of urinary protein (pyragallol red), immundetectable urinary albumin (immunoturbidimetry), and urinary total intact albumin (HPLC) after a single dose of 100 mg intravenous iron sucrose administered over 5 min. Fragmentation of urinary albumin and carbonylation of urinary proteins were assessed by immunoblotting. Results showed that iron infusion increased carbonylation of plasma and urinary proteins in a time-dependent manner. A transient increase in urinary excretion rates of total protein, immunodetectable urinary albumin, and total intact albumin was seen. Fragmentation and loss of immunoreactivity of albumin paralleled the changes in total protein excretion. In conclusion, fragmentation, loss of immunoreactivity, and oxidation of albumin in a time-dependent manner may underestimate the extent of injury with the immunoreactive microalbumin assay. Measurement of total intact albumin may better quantify acute renal injury.
蛋白尿是心血管和肾脏预后的一个极佳标志物。市面上用于检测尿液中可免疫检测的白蛋白的测试可能无法识别翻译后修饰的白蛋白，而这种修饰会使其无法被抗体检测到。此外，尚不清楚在急性肾损伤过程中白蛋白是否会降解为更小的片段，比如通过蛋白水解作用。在20名患有慢性肾病的男性中，我们在5分钟内静脉注射100毫克蔗糖铁单剂量后，测量了尿蛋白（邻苯三酚红法）、不可免疫检测的尿白蛋白（免疫比浊法）以及尿总完整白蛋白（高效液相色谱法）的排泄率。通过免疫印迹法评估尿白蛋白的片段化和尿蛋白的羰基化。结果显示，铁输注以时间依赖的方式增加了血浆和尿蛋白的羰基化。观察到总蛋白、可免疫检测的尿白蛋白和总完整白蛋白的尿排泄率出现短暂增加。白蛋白的片段化和免疫反应性丧失与总蛋白排泄的变化平行。总之，白蛋白的片段化、免疫反应性丧失和氧化呈时间依赖性，这可能会导致免疫反应性微量白蛋白检测低估损伤程度。测量总完整白蛋白可能能更好地量化急性肾损伤。
