Dept. Physiology and Biophysics, Weill Medical College of Cornell Univ., 1300 York Ave., New York, NY 10065, USA.
Am J Physiol Renal Physiol. 2010 Oct;299(4):F890-7. doi: 10.1152/ajprenal.00323.2010. Epub 2010 Aug 11.
Changes in apical surface expression of ion channels and transporters in the superficial rat renal cortex were assessed using biotinylation and immunoblotting during alterations in dietary K intake. A high-K diet increased, and a low-K diet decreased, both the overall and surface abundance of the β- and γ-subunits of the epithelial Na channel (ENaC). In the case of γ-ENaC, the effect was specific for the 65-kDa cleaved form of the protein. The overall amount of α-ENAC was also increased with increasing K intake. The total expression of the secretory K(+) channels (ROMK) increased with a high-K diet and decreased with a low-K diet. The surface expression of ROMK increased with high K intake but was not significantly altered by a low-K diet. In contrast, the amounts of total and surface protein representing the thiazide-sensitive NaCl cotransporter (NCC) decreased with increasing K intake. We conclude that modulation of K(+) secretion in response to changes in dietary K intake involves changes in apical K(+) permeability through regulation of K(+) channels and in driving force subsequent to alterations in both Na delivery to the distal nephron and Na(+) uptake across the apical membrane of the K(+) secretory cells.
在改变饮食钾摄入时，使用生物素化和免疫印迹评估了离子通道和转运体在大鼠肾皮质浅层顶膜表面表达的变化。高钾饮食增加，低钾饮食减少，上皮钠通道（ENaC）的β和γ亚基的整体和表面丰度。对于γ-ENaC，该作用是该蛋白 65 kDa 裂解形式特异性的。随着钾摄入的增加，α-ENAC 的总量也增加。分泌性 K(+)通道（ROMK）的总表达随着高钾饮食而增加，随着低钾饮食而减少。ROMK 的表面表达随着高钾摄入而增加，但低钾饮食并没有显著改变。相比之下，代表噻嗪类敏感的 NaCl 共转运体（NCC）的总蛋白和表面蛋白的量随着钾摄入的增加而减少。我们得出结论，对饮食钾摄入变化的钾分泌的调节涉及通过调节钾通道以及随后在远端肾单位中 Na 供应和 K(+)分泌细胞顶膜上的 Na(+)摄取的改变来调节顶膜的 K(+)通透性。
