Aldosterone stimulates activity and surface expression of NHE3 in human primary proximal tubule epithelial cells (RPTEC).
The steroid hormone aldosterone is a major regulator of extracellular volume and blood pressure. Aldosterone effectors are for example the epithelial Na(+) channel (ENaC), the Na(+)-K(+)-ATPase and the proximal tubule Na(+)/H(+) exchanger isoform 3 (NHE3). The aim of this study was to investigate whether aldosterone acts directly on proximal tubule cells to stimulate NHE3 and if so whether the EGF-receptor (EGFR) is involved. For this purpose, primary human renal proximal tubule cells were exposed to aldosterone. NHE3 activity was determined from Na(+)- dependent pH-recovery, NHE3 surface expression was determined by biotinylation and immunoblotting. EGFR-expression was assessed by ELISA. pH(i)- measurements revealed an aldosterone-induced increase in NHE3 activity, which was inhibited by the mineralocorticoid receptor blocker spironolactone and by the EGFR-kinase inhibitor AG1478. Immunoprecipitation and immunoblot analysis showed an aldosterone-induced increase in NHE3 surface expression, which was also inhibited by spironolactone and AG1478. Furthermore, aldosterone enhanced EGFR-expression. In conclusion, aldosterone stimulates NHE3 in human proximal tubule cells. The underlying mechanisms include AG1478 inhibitable kinase and are paralleled by enhanced EGFR expression, which could be compatible with EGF-receptor-pathway-dependent surface expression and activity of NHE3 in human primary renal proximal tubule epithelial cells.
Institute of Physiology, University of Wuerzburg, Germany. karina.drumm@gmx.de
Karina
K
Drumm
Theresia R
TR
Kress
Birgit
B
Gassner
Alexander W
AW
Krug
Michael
M
Gekle
D000450:Aldosterone / Q000494:pharmacology*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D011799:Quinazolines; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology
D004791:Enzyme Inhibitors; D011799:Quinazolines; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D020032:Tyrphostins; C101044:RTKI cpd; D000450:Aldosterone; D066246:ErbB Receptors