Na⁺, Cl⁻, Ca²⁺ and Zn²⁺ transport by fish gills: retrospective review and prospective synthesis

Abstract

The secondary active Cl(-) secretion in seawater (SW) teleost fish gills and elasmobranch rectal gland involves basolateral Na(+),K(+)-ATPase and NKCC, apical membrane CFTR anion channels, and a paracellular Na(+)-selective conductance. In freshwater (FW) teleost gill, the mechanism of NaCl uptake is more controversial and involves apical V-type H(+)-ATPase linked to an apical Na(+) channel, apical Cl(-)-HCO-3 exchange and basolateral Na(+),K(+)-ATPase. Ca(2+) uptake (in FW and SW) is via Ca(2+) channels in the apical membrane and Ca(2+)-ATPase in the basolateral membrane. Mainly this transport occurs in mitochondria rich (MR) chloride cells, but there is a role for the pavement cells also. Future research will likely expand in two major directions, molded by methodology: first in physiological genomics of all the transporters, including their expression, trafficking, operation, and regulation at the molecular level, and second in biotelemetry to examine multivariable components in behavioral physiological ecology, thus widening the integration of physiology from the molecular to the environmental levels while deepening understanding at all levels.

Ion uptake and acid secretion in zebrafish (Danio rerio)

“…Recently, higher protein expression analysed by an anti-rat ClC3 antibody was found in FW pufferfish gills than in SW ones (Tang and Lee, 2007). On the other hand, a cystic fibrosis transmembrane conductance regulator (CFTR) was also proposed to be a candidate for basolateral Cl -exit based on its basolateral localization in pavement and MR cells in killifish operculum (Marshall, 2002). In NCC cells, basolateral NKA may provide the intracellular negative gradient for driving the basolateral Cl -channels to transport Cl -out of NCC cells, as in mammalian DCT cells.…”

The African Lungfish (Protopterus dolloi): Ionoregulation and Osmoregulation in a Fish out of Water

“…An empty chamber containing the same volume of water but spiked with 22 Na ϩ and/or 36 Cl Ϫ was used as a control. Because rehydration of the gills, a main site of ion regulation in most fish (Perry 1997;Marshall 2002), could also alter ion movements after reimmersion, recovery experiments in water that were similar to those described for 3 H-H 2 O (above) were performed to track ion movements after 4 wk of air exposure. In these experiments, water samples were taken at 0, 2, 4, 8, 12, 16, and 24 h after reimmersion.…”

“…Inspection of the electron micrographs and immunohistochemistry of the skin and gills of P. annectens (Sturla et al 2001) suggests the MR cells are fewer in number and size compared to teleosts (Perry 1997;Marshall 2002). These observations, combined with the lungfish's reduced gill (Laurent et al Burggren and Johansen 1986), suggested that P. dolloi would have low basal rates of ion uptake.…”

“…In most freshwater fish species, the gills are the major site of ion exchange (Perry 1997;Marshall 2002), but they are also the major route of water entry due to the large surface area generated by numerous filaments containing secondary lamellae (Evans 1979). The gills of lungfish, however, are greatly reduced and characterized by a lack of gill filaments and secondary lamellae on the anterior gill arches and relatively low numbers of these structures on the posterior arches (Laurent et al 1978;Burggren and Johansen 1986).…”

Differential regulation of sodium–potassium pump isoforms during smolt development and seawater exposure of Atlantic salmon

“…The sodium gradient is then used by a Na + /K + /2Cl -co-transporter (NKCC1) to bring chloride into the cell. Chloride then leaves the cells on a favorable electrochemical gradient through an apical chloride channel, a homolog of the cystic fibrosis transmembrane conductance regulator (CFTR) (Marshall, 2002). In addition to providing the electrochemical gradient for chloride secretion, NKA also pumps sodium into the paracellular space where sodium leaves through leaky tight junctions on a favorable electrochemical gradient.…”