Lysosome distribution and cathepsin B and L activity along the rabbit proximal tubule.
Lysosome distribution and cathepsin B and L activity along the rabbit proximal tubule.
复制标题
沿兔近曲小管的溶酶体分布和组织蛋白酶 B 和 L 活性。
DOI：
10.1152/ajprenal.1987.253.6.f1290
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Park,CH
中科院分区：
文献类型：
--
作者：
Madsen,KM;Park,CH
近端小管中的溶酶体-空泡系统负责肾小球滤液中蛋白质的重吸收和降解。在这项研究中，我们绘制了兔近端小管溶酶体蛋白酶组织蛋白酶B和L的活性，并将组织蛋白酶活性与近端小管三段溶酶体和内吞噬空泡的体积进行了比较。使用两种合成底物，一种专门用于组织蛋白酶B，另一种专门用于组织蛋白酶B和l，对单个小管进行解剖和荧光测定。组织蛋白酶活性沿着近端小管的分布与每种底物是相同的，但当每毫米小管表达时，活性水平有两到三倍的差异。酶活性在S1段对应的初始4-5 mm较高，而在直段则下降至S1值的约20%。形态计量学分析显示，每毫米小管中溶酶体和内吞液泡的体积在S1节段明显大于S2和S3节段。这些结果表明，正常情况下，兔肾中蛋白质降解的主要部位是近端小管的起始4-5 mm，与S1段相对应，是已知的蛋白质重吸收的主要部位。
The lysosomal-vacuolar system in the proximal tubule is responsible for reabsorption and degradation of proteins from the glomerular filtrate. In this study we mapped the activity of the lysosomal proteinases, cathepsins B and L, along the rabbit proximal tubule and compared cathepsin activities with the volume of lysosomes and endocytic vacuoles in the three segments of the proximal tubule. Individual tubules were dissected and assayed fluorometrically using two synthetic substrates, one specific for cathepsin B and a second for cathepsins B and L. The distribution of cathepsin activity along the proximal tubule was the same with each substrate, but there was a two- to threefold difference in the level of activity when expressed per millimeter of tubule. Enzyme activities were high in the initial 4-5 mm corresponding to the S1 segment and decreased in the pars recta to approximately 20% of the S1 value. Morphometric analysis revealed that the volumes of lysosomes and endocytic vacuoles per millimeter of tubule were significantly greater in the S1 segment than in the S2 and S3 segments. These findings suggest that the main site of protein degradation in the rabbit kidney under normal conditions is the initial 4-5 mm of the proximal tubule which corresponds to the S1 segment and is known to be a major site of protein reabsorption.