Rastegar A, Biemesderfer D, Kashgarian M, Hayslett J P
Kidney Int. 1980 Sep;18(3):293-301. doi: 10.1038/ki.1980.139.
Chronic potassium loading results in an increased capacity of the distal nephron to secrete potassium. The cellular mechanism for this adaptation has been correlated to an increase in the activity of sodium-potassium-ATPase. Because adaptation may be dependent on the greater availability of potassium pumps in the basolateral membrane, a stereologic analysis of the membrane surface area was performed to determine whether the apparent increase in pump sites was due to an increase in cell membrane surface. With potssium adaptation, the number of microplicated cells in the outer medulla was reduced from 31 to 18%. There was a marked increase in the basolateral infolding of principal cells, and membrane surface increased by 32%. In papillary collecting duct cells, the basolateral membrane surface was unchanged but the surface density of the luminal membrane increased by 50%. These observations suggest that amplification of the basolateral cell membrane to increase the number of potassium pump sites per cell plays an important role in the mechanism of potassium adaptation in the outer medulla. A different mechanism involving the luminal membrane operates in the papillary collecting duct. Structural alterations in cell membrane surfaces are thus related to the regulation of the epithelial transport of electrolytes.
长期钾负荷会导致远端肾单位分泌钾的能力增强。这种适应性变化的细胞机制与钠钾 - ATP酶活性增加有关。由于这种适应性变化可能依赖于基底外侧膜上钾泵数量的增加，因此进行了膜表面积的体视学分析，以确定泵位点的明显增加是否是由于细胞膜表面积增加所致。钾适应后，外髓中微褶细胞的数量从31%减少至18%。主细胞的基底外侧内褶显著增加，膜表面积增加了32%。在乳头集合管细胞中，基底外侧膜表面积未变，但管腔膜的表面密度增加了50%。这些观察结果表明，基底外侧细胞膜的扩增以增加每个细胞的钾泵位点数量，在外髓钾适应机制中起重要作用。乳头集合管则通过涉及管腔膜的不同机制发挥作用。细胞膜表面的结构改变因此与上皮细胞电解质转运的调节相关。
