Hartwig J H, Brown D, Ausiello D A, Stossel T P, Orci L
Hematology Oncology Unit, Massachusetts General Hospital, Boston 02129.
J Histochem Cytochem. 1990 Aug;38(8):1145-53. doi: 10.1177/38.8.2164058.
Vasopressin regulates transepithelial osmotic water permeability in the kidney collecting duct and in target cells in other tissues. In the presence of hormone, water channels are inserted into an otherwise impermeable apical plasma membrane and the apical surface of these cells is dramatically remodelled. Because cytochalasin B and D greatly reduce the response of these cells to vasopressin, actin filaments are believed to participate in the events leading to an increase in transepithelial water permeability. Modulation of the actin filamentous network requires the concerted action of specific actin regulatory proteins, and in the present study we used protein A-gold immunocytochemistry to localize two important molecules, gelsolin and actin binding protein (ABP), in epithelial cells of the kidney inner medulla. Gelsolin and, to a lesser extent, ABP were concentrated in clusters in the apical cell web of principal cells of the collecting duct. Aggregates of gold particles were often associated with the cytoplasmic side of plasma membrane regions forming surface extensions or microvilli. The basolateral plasma membrane was labeled to a much lesser extent than the apical plasma membrane. In the thin limbs of Henle, ABP was localized over the apical plasma membrane in ascending limbs, but gelsolin labeling was weak in these cells. In thin descending limbs, the pattern of labeling was completely reversed, with abundant apical gelsolin labeling but only weak ABP immunolabeling. Although the significance of the distribution of actin regulatory proteins in thin limbs is unknown, the abundance and the predominantly apical polarization of both ABP and gelsolin in principal cells of the collecting duct is consistent with a role of the actin cytoskeleton in the mechanism of vasopressin actin.
血管加压素调节肾集合管及其他组织中靶细胞的跨上皮渗透水通透性。在激素存在的情况下，水通道插入原本不可渗透的顶端质膜，这些细胞的顶端表面会发生显著重塑。由于细胞松弛素B和D能大大降低这些细胞对血管加压素的反应，因此认为肌动蛋白丝参与了导致跨上皮水通透性增加的过程。肌动蛋白丝状网络的调节需要特定肌动蛋白调节蛋白的协同作用，在本研究中，我们使用蛋白A-金免疫细胞化学法在肾内髓质上皮细胞中定位两种重要分子，凝溶胶蛋白和肌动蛋白结合蛋白（ABP）。凝溶胶蛋白以及程度稍轻的ABP集中在集合管主细胞顶端细胞网的簇中。金颗粒聚集体常与形成表面延伸或微绒毛的质膜区域的胞质侧相关。基底外侧质膜的标记程度远低于顶端质膜。在髓袢细段，ABP定位于升支的顶端质膜上，但这些细胞中凝溶胶蛋白的标记较弱。在细降支中，标记模式完全相反，顶端凝溶胶蛋白标记丰富，但ABP免疫标记较弱。虽然肌动蛋白调节蛋白在细段中的分布意义尚不清楚，但ABP和凝溶胶蛋白在集合管主细胞中的丰富性和主要的顶端极化与肌动蛋白细胞骨架在血管加压素作用机制中的作用一致。
