Na(+)/H(+) antiporter that extrudes sodium in exchange for external protons (PubMed:15107534). Can also transport lithium (PubMed:15107534). 3 H(+)(out) + 2 Na(+)(in) = 3 H(+)(in) + 2 Na(+)(out) Inhibited by amiloride. Optimum pH is 7.5-8.5. Activity decreases sharply below pH 7.0 and is null at pH 6.5. Belongs to the NhaB Na(+)/H(+) (TC 2.A.34) antiporter family.