Background: In this study, the mechanism of the rapid non-genomic effect of aldosterone on Na<sup>+</sup>/H<sup>+</sup> exchanger (NHE)-mediated intracellular pH (pH<sub>i</sub>) 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<sub>4</sub>Cl was used to induce the acid load. Results: Aldosterone (10 n M) induced a rapid (<5 min) concentration-dependent increase in pH<sub>i</sub> recovery in M-1 cells, an effect mimicked by its precursor deoxycorticosterone (1 n M). This response was unaffected by the mineralocorticoid receptor (MR) antagonist spironolactone (10 µ M) but was significantly reduced by the NHE antagonists 5′-(N-ethyl- N-isopropyl)amiloride (EIPA) (20 µ M) and cariporide (1 µ M). The PKC inhibitor chelerythrine chloride (1 µ M) significantly attenuated the aldosterone-induced increase in NHE1 activity. HBDDE (80 µ M), a PKC<sub>α</sub> inhibitor, inhibited the rapid aldosterone effect whereas rottlerin (15 µ M), a PKC<sub>δ</sub> antagonist, did not. The glucocorticoid receptor agonists hydrocortisone (1 µ M) and dexamethasone (100 n M) decreased NHE activity, whereas the synthetic mineralocorticoid fludrocortisone (1 n M) had no significant effect. MAPK inhibition using PD98059 (25 µ M) 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. Conclusion: Aldosterone causes a rapid non-genomic increase in NHE1 activity in M-1 cells via a PKC<sub>α </sub>/MAPK pathway independent of the classical MR.