Table 2.

List of ion transporters identified by the present review in the physiological literature on freshwater fish, Crustacea, aquatic insects, and Mollusca

Transporter	Acronym	Function	Gene family
V-type H+-ATPase	VHA	Transports H+ across apical or basolateral membranes	ATPase H+-transporting subunits
Apical Na+-channel	—	Transports Na+ across usually apical membranes	?
Acid sensing ion channel	ASIC	Possibly transports Na+ across usually apical membranes	Acid sensing ion channel subunits
Na+/H+-exchanger	NHE	Exchanges Na+ for H+ across apical membranes	Solute carrier family 9
P-type Na+/K+-ATPase	NKA	Exchanges Na+ and K+ across basolateral membranes	ATPase Na+/K+-transporting subunits
K+-channel	KC	Transports K+ across basolateral membranes	K+ voltage-gated channel
Na+/HCO3−-cotransporter	NBC	Transports Na+ and HCO3− across basolateral membranes	Solute carrier family 4
Cl−/HCO3−-exchanger	AE	Exchanges Cl− for HCO3− across apical membranes	Solute carrier family 4
Epithelial Ca2+-channel	ECaC	Transports Ca2+ across apical membranes	Transient receptor potential cation channel
Ca2+-ATPase	PMCA	Transports Ca2+ across basolateral membranes	ATPase Ca2+ transporting
Cl−-channel	—	Transports Cl− across basolateral membranes	?
Carbonic anhydrase	CA	Catalyzes the hydrolysis of CO2 to form H+ and HCO3−	Carbonic anhydrase
Na+/Ca2+-exchanger	NCX	Exchanges Na+ for Ca2+ across basolateral membranes	Solute carrier family 8
Na+/Cl−-cotransporter	NCC	Transports Na+ and Cl− across apical membranes	Solute carrier family 12
Na+/K+/Cl−-cotransporter	NKCC	Transports Na+, K+ and Cl− across apical membranes	Solute carrier family 12
H+/2Na+(or Ca2+)-exchanger	H2Na(Ca)E	Exchanges 2Na+ or Ca2+ for H+ across apical membranes	Solute carrier family 9
Anion/SO42−-antiporter	—	Exchanges another anion for SO42−across apical membranes	?

ATPase = adenosinetriphosphatase; V-type = vacuolar-type; P-type = Purkinje cells-type; ? = not sufficiently characterized to place in a gene family.