The use of amiloride to uncouple branchial sodium and proton fluxes in the brown trout, Salmo trutta

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

“…In addition to blocking Na ϩ absorption (see sect. VB1), amiloride has been shown to inhibit net-acid excretion when placed in water irrigating the gills of rainbow trout, brown trout, European flounder, killifish, little skate, and longhorn sculpin (74,108,111,173,407,522,575,576). However, these results do not distinguish between the two acid secretion mechanisms, because amiloride inhibits Na ϩ transport by NHEs and ENaC (39).…”

Modulation of Rh glycoproteins, ammonia excretion and Na+ fluxes in three freshwater teleosts when exposed chronically to high environmental ammonia

“…If these changes signify an increased H + efflux, this scenario predicts that Na + uptake may become partially uncoupled from H + flux and ammonia excretion under these circumstances. It is also tempting to speculate that during HEA exposure, NH 4 + may act like a low dose of amiloride, limiting Na + uptake, while at the same time H + efflux and boundary layer acidification for trapping of NH 3 efflux can still occur (Nelson et al, 1997). Moreover, upregulation of NHE-2 would serve to maintain some degree of Na + uptake (Zimmer et al, 2010).…”

Gene expression of Na+/H+ exchanger in zebrafish H+-ATPase-rich cells during acclimation to low-Na+ and acidic environments

“…On the other hand, amiloride and EIPA, which inhibit Na ϩ uptake, had no effect on net acid secretion in FW rainbow trout, brown trout, or European flounder (25,29,30,34,44). Boisen et al (4) reported that responses of Na ϩ uptake to several inhibitors, including bafilomycin, ethoxzolamide, and amiloride, were variable in zebrafish acclimated to soft water and hard water.…”