Aldosterone rapidly activates Na+/H+ exchange in M-1 cortical collecting duct cells via a PKC-MAPK pathway.
BACKGROUND
In this study, the mechanism of the rapid non-genomic effect of aldosterone on Na(+)/H(+) exchanger (NHE)-mediated intracellular pH (pH(i)) recovery from an acid load in murine M-1 cortical collecting duct cells was assessed.


METHODS
Spectrofluorescence microscopy and Western blot analysis was carried out and NH(4)Cl was used to induce the acid load.


RESULTS
Aldosterone (10 nM) induced a rapid (<5 min) concentration-dependent increase in pH(i) recovery in M-1 cells, an effect mimicked by its precursor deoxycorticosterone (1 nM). This response was unaffected by the mineralocorticoid receptor (MR) antagonist spironolactone (10 microM) but was significantly reduced by the NHE antagonists 5'-(N-ethyl- N-isopropyl)amiloride (EIPA) (20 microM) and cariporide (1 microM). The PKC inhibitor chelerythrine chloride (1 microM) significantly attenuated the aldosterone-induced increase in NHE1 activity. HBDDE (80 microM), a PKC(alpha) inhibitor, inhibited the rapid aldosterone effect whereas rottlerin (15 microM), a PKC(delta) antagonist, did not. The glucocorticoid receptor agonists hydrocortisone (1 microM) and dexamethasone (100 nM) decreased NHE activity, whereas the synthetic mineralocorticoid fludrocortisone (1 nM) had no significant effect. MAPK inhibition using PD98059 (25 microM) significantly attenuated the rapid aldosterone effect; Western blot analysis showed that aldosterone activation of ERK 1/2 was unaffected by pretreatment with spironolactone but was inhibited following chelerythrine chloride.


CONCLUSIONS
Aldosterone causes a rapid non-genomic increase in NHE1 activity in M-1 cells via a PKC(alpha )/MAPK pathway independent of the classical MR.
Markos
Farouk
F
Department of Physiology, University College Cork, Cork, Ireland.
Healy
Vincent
V
Harvey
Brian J
BJ
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D027682:Cation Transport Proteins / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D027682:Cation Transport Proteins; D008565:Membrane Proteins; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D000450:Aldosterone; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases