Bourbouze R, Baumann F C, Bonvalet J P, Farman N
Kidney Int. 1984 Apr;25(4):636-42. doi: 10.1038/ki.1984.68.
Total N-acetyl-beta-D-glucosaminidase (NAG) activity has been measured in microdissected glomeruli (G) and tubular segments [proximal convoluted tubule (PCT), pars recta (PR), medullary thick ascending limb (MAL), and cortical collecting tubule (CCT)] of the rabbit kidney, by a fluorimetric method using synthetic substrate. Selective activity of the isoenzyme NAG B was also determined. Isoenzyme profiles of NAG were obtained by electrofocusing on each segment. Characterization of the isoenzymes was performed by chromatofocusing and thermosensitivity experiments on PCT. Total NAG activity, mainly composed of NAG A, was low in glomeruli and two and one-half to four times higher in PCT than in other segments, in which comparable activities were found. NAG B was detectable all along the nephron. It represented a very small fraction of total NAG, except in PCT where it was more abundant (20 to 30%). Electrofocusing revealed the presence of a minor form (NAG I) all along the nephron. Chromatofocusing and thermosensitivity studies indicated that NAG I could represent imperfectly solubilized NAG A rather than a well defined entity. From these results, it could be suggested that the reported increase in urinary excretion of NAG B after renal injury may reflect the intensity of proximal tubular lesions.
采用荧光法，使用合成底物，测定了兔肾经显微切割的肾小球（G）和肾小管各节段[近端曲管（PCT）、直部（PR）、髓质厚升支（MAL）和皮质集合管（CCT）]中的总N - 乙酰 - β - D - 氨基葡萄糖苷酶（NAG）活性。还测定了NAG B同工酶的选择性活性。通过对每个节段进行等电聚焦获得NAG的同工酶谱。通过对近端曲管进行色谱聚焦和热敏感性实验对同工酶进行表征。总NAG活性主要由NAG A组成，在肾小球中较低，在近端曲管中比其他节段高2.5至4倍，其他节段的活性相当。在整个肾单位中均可检测到NAG B。它在总NAG中所占比例非常小，近端曲管除外，在近端曲管中它更为丰富（20%至30%）。等电聚焦显示在整个肾单位中存在一种次要形式（NAG I）。色谱聚焦和热敏感性研究表明，NAG I可能代表溶解不完全的NAG A，而不是一个明确的实体。从这些结果可以推测，肾损伤后报道的NAG B尿排泄增加可能反映近端肾小管损伤的程度。
