Haase W, Koepsell H
Max-Planck-Institut für Biophysik, Frankfurt am Main/Bundesrepublik Deutschland.
Eur J Cell Biol. 1989 Apr;48(2):360-74.
The localization of Na+-cotransport proteins in cortex and outer medulla of rat kidney was investigated with five monoclonal antibodies. Recently, it was found that these antibodies altered Na+-D-glucose cotransport and/or Na+-dependent high affinity phlorizin binding in pig kidney cortex and that three of these antibodies interacted also with Na+-cotransporters for lactate, L-alanine and/or L-glutamate (Koepsell, H., K. Korn, A. Raszeja-Specht, S. Bernotat-Danielowski, D. Ollig, J. Biol. Chem. 263, 18,419-18,429 (1988]. In pig and rat the monoclonal antibodies bind to two brush-border membrane polypeptides with identical molecular weights and isoelectric points of 75,000 and pI 5.5, and 47,000 and pI 5.4. These polypeptides have been previously identified as components of the porcine renal Na+-D-glucose cotransporter (Neeb, M., U. Kunz, H. Koepsell, J. Biol. Chem. 262, 10,718-10,727 (1987] and may also be part of other Na+-cotransporters. The electron microscopic localization of antibody binding was demonstrated by protein A-gold labeling on ultrathin plastic sections. Three antibodies bound to brush-border membranes of proximal convoluted and straight tubules. In the proximal convoluted tubules all antibodies reacted with apical endocytic vacuoles, apical dense tubules and lysosomes. Since dense tubules are supposed to originate from endocytic vacuoles and to fuse with brush-border membranes the data suggest recycling of Na+-cotransporters in the proximal convoluted tubule. In the outer medulla two antibodies bound to apical membranes of descending thin limbs (DTL) of short loops of Henle and to apical and basal membranes of DTL of long loops of Henle. Three antibodies bound to apical membranes of collecting ducts. These data indicate that Na+-cotransporters or homologous proteins exist beyond the proximal tubule.
利用五种单克隆抗体研究了大鼠肾皮质和外髓中钠协同转运蛋白的定位。最近发现，这些抗体改变了猪肾皮质中的钠 - D - 葡萄糖协同转运和/或钠依赖性高亲和力根皮苷结合，并且其中三种抗体还与乳酸、L - 丙氨酸和/或L - 谷氨酸的钠协同转运体相互作用（Koepsell, H., K. Korn, A. Raszeja - Specht, S. Bernotat - Danielowski, D. Ollig, J. Biol. Chem. 263, 18,419 - 18,429 (1988]）。在猪和大鼠中，单克隆抗体与两种刷状缘膜多肽结合，其分子量相同，等电点分别为75,000和pI 5.5，以及47,000和pI 5.4。这些多肽先前已被鉴定为猪肾钠 - D - 葡萄糖协同转运体的组成部分（Neeb, M., U. Kunz, H. Koepsell, J. Biol. Chem. 262, 10,718 - 10,727 (1987]），也可能是其他钠协同转运体的一部分。通过在超薄塑料切片上进行蛋白A - 金标记证明了抗体结合的电子显微镜定位。三种抗体与近曲小管和直小管的刷状缘膜结合。在近曲小管中，所有抗体都与顶端内吞泡、顶端致密小管和溶酶体发生反应。由于致密小管被认为起源于内吞泡并与刷状缘膜融合，这些数据表明近曲小管中钠协同转运体的再循环。在外髓中，两种抗体与短袢髓袢降支细段（DTL）的顶端膜结合，以及与长袢髓袢降支细段的顶端和基底膜结合。三种抗体与集合管的顶端膜结合。这些数据表明在近端小管之外存在钠协同转运体或同源蛋白。
