The effect of environmental hypercapnia and salinity on the expression of NHE-like isoforms in the gills of a euryhaline fish (Fundulus heteroclitus).

The current models for branchial acid excretion in fishes include Na(+)/H(+) exchange and the electrogenic excretion of H+ via H+-ATPase. The predominant route of acid excretion in some freshwater fishes is thought to be via the H+-ATPase/Na+ channel system. The euryhaline Fundulus heteroclitus may not fit this profile even when adapted to freshwater (FW).