Gröne H J, Walli A K, Gröne E, Krämer A, Clemens M R, Seidel D
Department of Pathology, University Hospital, Göttingen, Federal Republic of Germany.
Kidney Int. 1990 Jun;37(6):1449-59. doi: 10.1038/ki.1990.135.
Various pathological disorders are accompanied by the deposition of lipids into glomerular cells. To gain insight into these disorders, it is essential to know if glomerular cells possess lipoprotein receptors. We therefore characterized the activity of lipoprotein receptors in cultured epithelial cells of the human glomerulus. Podocytes were chosen as they are directly exposed to lipoproteins in pathological states like in glomerular proteinuria (such as, nephrotic syndrome). Isolated human glomeruli (purity greater than 95%) were incubated in buffered RPMI 1640 medium supplemented with 20% heat-inactivated fetal bovine serum at 37 degrees C and 5% CO2. Outgrowing cells were vimentin and keratin positive. Monolayer cultures of human glomerular epithelial cells upon incubation in lipoprotein deficient serum for 48 hours expressed a receptor-dependent uptake of lipoproteins. These cells showed about 10% of the maximal capacity for LDL uptake as compared to fibroblasts; however, the Km values for binding, internalization and degradation were similar in the cultures of glomerular epithelial cells and fibroblasts. The Km values for degradation of LDL, chylomicron remnants, beta-VLDL from cholesterol-fed rabbits and VLDL from familial LCAT-deficiency patients were 14.2, 4.9, 2.9, 4.5 micrograms protein/ml medium, respectively, for glomerular epithelial cells. The avid uptake of 125I-labeled apo E-containing lipoproteins was further substantiated by their poor displacement by a 25-fold excess of unlabeled LDL and their ability to down regulate the apo B,E receptor activity. LDL as well as beta-VLDL were able to suppress the incorporation of 14C acetate into sterols and to stimulate 3H-cholesterylester formation. These experiments show that cultured glomerular epithelial cells express lipoprotein receptor activity. Plasma concentrations of apo E-containing lipoproteins are increased in certain renal diseases (such as, nephrotic syndrome); these lipoproteins could be rapidly removed by glomerular epithelial cells and lead to lipid deposition in glomeruli.
多种病理紊乱伴有脂质在肾小球细胞中的沉积。为深入了解这些紊乱，了解肾小球细胞是否拥有脂蛋白受体至关重要。因此，我们对人肾小球培养上皮细胞中的脂蛋白受体活性进行了表征。选择足细胞是因为它们在诸如肾小球蛋白尿（如肾病综合征）等病理状态下直接暴露于脂蛋白。将分离的人肾小球（纯度大于95%）在补充有20%热灭活胎牛血清的缓冲RPMI 1640培养基中于37℃和5%二氧化碳条件下孵育。生长出的细胞波形蛋白和角蛋白呈阳性。人肾小球上皮细胞单层培养物在脂蛋白缺乏血清中孵育48小时后表现出受体依赖性的脂蛋白摄取。与成纤维细胞相比，这些细胞显示出约10%的低密度脂蛋白摄取最大能力；然而，肾小球上皮细胞和成纤维细胞培养物中结合、内化和降解的米氏常数相似。对于肾小球上皮细胞，低密度脂蛋白、乳糜微粒残粒、胆固醇喂养兔的β-极低密度脂蛋白和家族性卵磷脂胆固醇酰基转移酶缺乏患者的极低密度脂蛋白降解的米氏常数分别为14.2、4.9、2.9、4.5微克蛋白质/毫升培养基。125I标记的含载脂蛋白E的脂蛋白的 avid摄取通过以下事实进一步得到证实：25倍过量的未标记低密度脂蛋白对其置换作用较差，以及它们下调载脂蛋白B、E受体活性的能力。低密度脂蛋白以及β-极低密度脂蛋白能够抑制14C乙酸盐掺入固醇并刺激3H-胆固醇酯形成。这些实验表明培养的肾小球上皮细胞表达脂蛋白受体活性。在某些肾脏疾病（如肾病综合征）中，含载脂蛋白E的脂蛋白的血浆浓度会升高；这些脂蛋白可被肾小球上皮细胞迅速清除并导致脂质在肾小球中沉积。
