Segregation of ferritin in glomerular protein absorption droplets.
Segregation of ferritin in glomerular protein absorption droplets.
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DOI：
10.1083/jcb.7.2.297
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发表时间：
1960-04
期刊：
影响因子：
--
通讯作者：
PALADE GE
中科院分区：
文献类型：
--
作者：
FARQUHAR MG;PALADE GE
铁蛋白被用作示踪剂来研究蛋白质被肾小球毛细血管的内脏上皮分离成液滴的机制。在肾小球正常和aminoproside肾病大鼠铁蛋白分子引入到一般循环渗透内皮开口，并在基底膜的不同水平。肾病患者和对照组之间的显著差异仅见于上皮中铁蛋白的含量。在正常动物中，在限制足突的细胞膜的小内陷中、在上皮中的微小囊泡内或在偶尔的大空泡和致密体内观察到一些铁蛋白分子。在肾病患者中，上皮细胞胞饮明显，在所有时间点，在膜内陷和小胞质囊泡中观察到大量铁蛋白分子。经过较长的时间间隔，铁蛋白的浓度增加，在空泡，特别是在致密体或结构内的形态之间的空泡和致密体。在肾病动物中，沿着面向泌尿空间的上皮细胞表面经常遇到裂隙样腔或窦。其中一些鼻窦含有类似于填充致密体的物质，只是看起来不那么致密。研究结果表明，铁蛋白分子和其他可能穿透基底膜的蛋白质在胞饮小泡中被上皮细胞吸收，并通过小泡运输到较大的空泡中，随后通过进行性浓缩转化为致密体。然后致密体的内容物可能经历部分消化并被挤出到尿腔中，在那里分散。正常和肾病动物肾小球上皮细胞在蛋白质掺入和分离方面的活性相似，只是肾病中肾小球基底膜的渗透性大大增加，其速率明显较高。
Ferritin was used as a tracer to study the mechanism by which proteins are segregated into droplets by the visceral epithelium of glomerular capillaries. In glomeruli from both normal and aminonucleoside-nephrotic rats ferritin molecules introduced into the general circulation penetrated the endothelial openings and were seen at various levels in the basement membrane. Striking differences between nephrotic and controls were seen only in the amount of ferritin incorporated into the epithelium. In normal animals, a few ferritin molecules were seen in small invaginations of the cell membrane limiting the foot processes, within minute vesicles in the epithelium, or within occasional large vacuoles and dense bodies. In nephrotics, epithelial pinocytosis was marked, and numerous ferritin molecules were seen within membrane invaginations and in small cytoplasmic vesicles at all time points. After longer intervals, the concentration of ferritin increased in vacuoles and particularly within the dense bodies or within structures with a morphology intermediate between that of vacuoles and dense bodies. In nephrotic animals cleft-like cavities or sinuses were frequently encountered along the epithelial cell surface facing the urinary spaces. Some of these sinuses contained material resembling that filling the dense bodies except that it appeared less compact. The findings suggest that ferritin molecules—and presumably other proteins which penetrate the basement membrane—are picked up by the epithelium in pinocytotic vesicles and transported via the small vesicles to larger vacuoles which are subsequently transformed into dense bodies by progressive condensation. The content of the dense bodies may then undergo partial digestion and be extruded into the urinary spaces where it disperses. The activity of the glomerular epithelium in the incorporation and segregation of protein is similar in normal and nephrotic animals, except that the rate is considerably higher in nephrosis where the permeability of the glomerular basement membrane is greatly increased.