Cl⁻Uptake Mechanism in Freshwater‐Adapted Tilapia (Oreochromis mossambicus)

Abstract

In this study, the correlation between Cl(-) influx in freshwater tilapia and various transporters or enzymes, the Cl(-)/HCO(3)(-) exchanger, Na(+),K(+)-ATPase, V-type H(+)-ATPase, and carbonic anhydrase were examined. The inhibitors 2x10(-4) M ouabain (a Na(+),K(+)-ATPase inhibitor), 10(-5) M NEM (a V-type H(+)-ATPase inhibitor), 10(-2) M ACTZ (acetazolamide, a carbonic anhydrase inhibitor), and 6x10(-4) M DIDS (a Cl(-)/HCO(3)(-) exchanger inhibitor) caused 40%, 60%-80%, 40%-60%, and 40%-60% reduction in Cl(-) influx of freshwater tilapia, respectively. The inhibitor 2x10(-4) M ouabain also caused 50%-65% inhibition in gill Na(+),K(+)-ATPase activity. Western blot results showed that protein levels of gill Na(+),K(+)-ATPase, V-type H(+)-ATPase, and carbonic anhydrase in tilapia acclimated in low-Cl(-) freshwater were significantly higher than those acclimated to high-Cl(-) freshwater. Based on these data, we conclude that Na(+),K(+)-ATPase, V-H(+)-ATPase, the Cl(-)/HCO(3)(-) exchanger, and carbonic anhydrase may be involved in the active Cl(-) uptake mechanism in gills of freshwater-adapted tilapia.

The role of branchial carbonic anhydrase in acid-base regulation in rainbow trout (Oncorhynchus mykiss)

“…It has long been postulated that branchial CA contributes to ionic and acid-base regulation in freshwater teleost fish by catalyzing the hydration of CO 2 within the branchial epithelium to the acid-base equivalents, H + and HCO 3 -, that are used as counter-ions for Na + and Cl -uptake, respectively (reviewed by Perry and Laurent, 1990;Goss et al, 1992Goss et al, , 1995Henry and Swenson, 2000;Claiborne et al, 2002;Perry et al, 2003;Hirose et al, 2003;Evans et al, 2005). The contribution of branchial CA to ion uptake is supported by the significant reductions in Na + or Cl -influx that have been documented in most, although not all (Kerstetter and Kirschner, 1972), studies following inhibition of branchial CA by acetazolamide in vivo (Maetz, 1956;Maetz and GarciaRomeu, 1964;Boisen et al, 2003;Chang and Hwang, 2004), in situ (Kerstetter et al, 1970) or in perfused gill preparations (Payan et al, 1975). Fewer studies have focused on the role of branchial CA in acid-base regulation.…”

“…Maetz, 1956;Maetz and Garcia-Romeu, 1964;Boisen et al, 2003;Chang and Hwang, 2004), experimental data for the role played by intracellular CA activity in acid-base regulation specifically are lacking. High levels of CA activity have been found in the gills of all fish species examined (reviewed by Perry and Laurent, 1990;Henry and Swenson, 2000).…”

The involvement of SLC26 anion transporters in chloride uptake in zebrafish (Danio rerio) larvae

“…Prior to the demonstration of pendrin (SLC26A4)-like immunoreactivity on the elasmobranch gill (Piermarini et al, 2001), it was generally considered that branchial Cl -/HCO 3 -exchange was accomplished by one or more members of the SLC4 gene family. This conclusion was reinforced by the results of studies utilizing immunocytochemistry (Wilson et al, 2000), in situ hybridization (Sullivan et al, 1996) and data obtained from pharmacological - (Epstein et al, 1973;Perry et al, 1981a;Chang and Hwang, 2004;Preest et al, 2005). With the benefit of hindsight, however, the results of these former studies are subject to reinterpretation.…”

Chloride channel ClC-3 in gills of the euryhaline teleost,Tetraodon nigroviridis: expression, localization and the possible role of chloride absorption

“…Half the water was changed every other day to maintain optimal water quality. Artificial waters for both the control and low-Cl groups were prepared by dissolving appropriate amounts of NaCl, Na 2 SO 4 , CaCl 2 and CaSO 4 in deionized water, according to the method described in previous studies and with little modification Chang and Hwang, 2004;Inokuchi et al, 2009 in the low-Cl group. The analysis of Na + and Ca 2+ concentrations of water samples was carried out using an inductively coupled plasma optic emission spectrometry (ICP-OES; Perkin Elmer Optima 2100DV, Waltham, MA, USA).…”