The Mechanism of Sodium and Chloride Uptake by the Gills of a Fresh-Water Fish, Carassius auratus

Abstract

A~STRaCT The addition of ammonium ions to the external medium results in an inhibition of the sodium influx and net uptake in Carassius auratus, while intraperitoneal injection of ammonium produces the opposite effect. The simultaneous chloride balance is not significantly affected by these treatments. The addition of bicarbonate ions to the external medium results in a reduction of the influx and net flux of chloride, while injection of bicarbonate produces the opposite effect. The simultaneous sodium balance is not significantly altered. The effects of the external additiom are reversible after elimination of the excess ammonium or bicarbonate ions by rinsing. Inhibition of carbonic anhydrase in the gill by injection of acetazoleamide produces a simultaneous inhibition of both sodium and chloride exchanges. These results confirm the hypothesis of an exchange of sodium for ammonium, and of bicarbonate for chloride across the gill. A tentative schematic representation of the ionic absorption mechanisms in the branchial cell of the fresh-water teleosts is given. Similarities with other biological membranes and especially with the renal tubule are pointed out.In the preceding publication (Garcla Romeu and Maetz, 1964) substantial evidence was advanced to show that in Carassius auratus the absorption of sodium and chloride ions by the gill is independent. Such independence can only be explained by the assumption that these ions are independently exchanged with endogenous ions. Krogh (1937Krogh ( , 1939 has suggested that the NH + and HCO~ ions might play this role. The work presented here is an attempt to verify this hypothesis.In support of the postulated sodium-ammonium exchange is the fact that the gill is the principal site for nitrogenous excretion in teleosts (Smith, 1929; I~o 9

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

“…Indeed, we are unaware of any isotope provider currently able to supply 36 Cl to North American researchers. The previous evidence implicating Cl -/HCO 3 -exchange as a mechanism for Cl -uptake in freshwater fish is overwhelming (Krogh, 1937;Krogh, 1938;Maetz and Garcia Romeu, 1964;De Renzis and Maetz, 1973;De Renzis, 1975;Braun et al, 2009) (reviewed by Marshall, 1995;Claiborne, 1998;Evans et al, 1999;Marshall, 2002;Perry et al, 2003a;Perry et al, 2003b;Evans et al, 2005;Perry and Gilmour, 2006;Marshall and Grosell, 2006;Tresguerres et al, 2006;Hwang and Lee, 2007;Evans, 2008). 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.…”

Carbonic anhydrase expression and CO2 excretion during early development in zebrafishDanio rerio

“…Cytosolic CA in the branchial epithelium catalyzes the hydration of CO 2 to H + and HCO 3 -that can then be used as counter-ions for, respectively Na + and Cl -uptake, transport processes that are critical for both ionic regulation and acid-base balance (reviewed by Evans et al, 2005;Perry and Gilmour, 2006;Tresguerres et al, 2006;Hwang and Lee, 2007;Gilmour and Perry, 2009). Correspondingly, inhibition of branchial CA reduces Na + and/or Cl -uptake (Maetz, 1956;Maetz and Garcia-Romeu, 1964;Kerstetter et al, 1970;Payan et al, 1975;Boisen et al, 2003;Chang and Hwang, 2004) as well as branchial net acid excretion (Georgalis et al, 2006).…”

Effect of urea introduced into feed on structural changes and mucopolisacharides content in branchial epithelium of rawbow trout (Salmo gairdneri Richardson)

“…Besides those substances take part in an active transport of ions and ammonium fnrough cell membranes (Whitelaw, 1975). For higher concentrations, ions excess is ibeing removed by diffusion (Maetz, 1964;Kniazieva, 1970). Putting excretion mechanisms in motion is attender!…”

“…Urea within the fish body is being included into aminoacids cycles (Kniazieva, 1970), with ammonium as a by-product of it. Ammonium is being actively expelled by the acid mucopolisaccharides by way of counter-exchange with sodium, or, in case of an excess, by way of diffusion (Maetz, 1964;Whitelaw, 1975). Pu tting in motion excretion mechanisms causes changes within the branchial epithelium microstructure.…”