Costigan M G, Rustom R, Bone J M, Shenkin A
Department of Clinical Chemistry, Royal Liverpool University Hospital, UK.
Clin Chim Acta. 1996 Nov 29;255(2):133-44. doi: 10.1016/0009-8981(96)06400-5.
In patients with proteinuria, indices of tubular damage are unreliable since filtered plasma enzymes could contribute to tubular enzymuria. Previous work has suggested the existence of various forms of the 'A' isoenzyme of N-acetyl-beta, D-glucosaminidase (NAG), one of which could be kidney specific and thus a useful marker of renal tubular damage. By using fast protein liquid chromatography, two forms of the 'A' isoenzyme, 'A1' and 'A2' were separated in human urine, plasma and kidney tissue. The isoenzyme profile in pathological urine resembled that seen in kidney tissue, the 'A2' isoenzyme predominating. The ratio A2/A1 in the urine of renal patients was significantly greater than in the plasma of renal patients, end-stage renal failure patients and healthy volunteers. There was no difference in the plasma ratios of the three groups studied. The clearances of total NAG, 'A1' and 'A2' isoenzymes were all greater than that of the lower molecular weight protein transferrin. This indicates that the origin of urinary NAG in patients with proteinuria is from the kidney itself. Thus, analysis of urinary NAG and its isoenzymes may be of benefit as an early predictor of renal tubular damage and may also be useful as a non-invasive indicator of disease progression.
在蛋白尿患者中，肾小管损伤指标不可靠，因为滤过的血浆酶可能导致肾小管酶尿。先前的研究表明存在多种形式的N - 乙酰 - β，D - 氨基葡萄糖苷酶（NAG）的“A”同工酶，其中一种可能是肾脏特异性的，因此是肾小管损伤的有用标志物。通过快速蛋白质液相色谱法，在人尿、血浆和肾组织中分离出两种“A”同工酶形式，即“A1”和“A2”。病理性尿液中的同工酶谱与肾组织中的相似，以“A2”同工酶为主。肾病患者尿液中的A2/A1比值显著高于肾病患者、终末期肾衰竭患者和健康志愿者血浆中的该比值。所研究的三组血浆比值无差异。总NAG、“A1”和“A2”同工酶的清除率均高于低分子量蛋白质转铁蛋白的清除率。这表明蛋白尿患者尿中NAG的来源是肾脏本身。因此，分析尿NAG及其同工酶可能有助于作为肾小管损伤的早期预测指标，也可能作为疾病进展的非侵入性指标。
