Dymowska, A.K., Boyle, D., Schultz, A.G., Goss, G.G. (2015) The role of acid-sensing ion channels (ASICs) in epithelial Na+ uptake in adult zebrafish (Danio rerio). The Journal of experimental biology. 218(Pt 8):1244-51.
Acid-sensing ion channels (ASICs) are epithelial Na(+) channels gated by external H(+). Recently, it has been demonstrated that ASICs play a role in Na(+) uptake in freshwater rainbow trout. The current paper investigated the potential involvement of ASICs in Na(+) transport in another freshwater fish species, the zebrafish (Danio rerio). Using molecular and histological techniques we found that asic genes and the ASIC4.2 protein are expressed in the gill of adult zebrafish. Immunohistochemistry revealed that mitochondrion-rich cells positive for ASIC4.2 do not co-localize with Na(+)/K(+)-ATPase (NKA)-rich cells, but co-localize with cells expressing vacuolar-type H(+)-ATPase (VHA). Furthermore, pharmacological inhibitors of ASIC and Na(+)/H(+)-exchanger (NHEs) significantly reduced uptake of Na(+) in adult zebrafish exposed to low Na(+) media, but did not cause the same response in individuals exposed to ultra-low Na(+) water. Our results suggest that in adult zebrafish ASICs play a role in branchial Na(+) uptake in media with low Na(+) concentrations and that mechanisms used for Na(+) uptake by zebrafish may depend on the Na(+) concentration in the acclimation media.