Teleost fishes are able to acclimatize to seawater by secreting excess NaCl by means of specialized "ionocytes" in the gill epithelium. Antibodies against Na(+)/K(+)-ATPase (NKA) have been used since 1996 as a marker for identifying branchial ionocytes. Immunohistochemistry of NKA by itself and in combination with Na(+)/K(+)/2Cl(-) cotransporter and CFTR Cl(-) channel provided convincing evidence that ionocytes are functional during seawater acclimation, and also revealed morphological variations in ionocytes among teleost species. Recent development of antibodies to freshwater- and seawater-specific isoforms of the NKA alpha-subunit has allowed functional distinction of ion absorptive and secretory ionocytes in Atlantic salmon. Cutaneous ionocytes of tilapia embryos serve as a model for branchial ionocytes, allowing identification of 4 types: two involved in ion uptake, one responsible for salt secretion and one with unknown function. Combining molecular genetics, advanced imaging techniques and immunohistochemistry will rapidly advance our understanding of both the unity and diversity of ionocyte function and regulation in fish osmoregulation.
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http://dx.doi.org/10.1016/j.resp.2012.07.019 | DOI Listing |
Comp Biochem Physiol Part D Genomics Proteomics
December 2024
Department of Biology, Skidmore College, 815 N. Broadway, Saratoga Springs, NY 12866, USA. Electronic address:
Along the east coast of North America, mummichogs (Fundulus heteroclitus) are subjected to a broad range of salinities in their nearshore habitats. However, there is a paucity of information regarding the molecular and cellular processes that mummichogs (and other highly osmotolerant fishes) engage to survive environmental salinities greater than seawater (SW). To reveal branchial processes underlying their extraordinarily broad salinity tolerance, we performed an RNA-Seq analysis to identify differentially expressed genes (DEGs) in mummichogs residing in 3, 35, and 105 ppt conditions.
View Article and Find Full Text PDFAm J Physiol Regul Integr Comp Physiol
November 2024
Department of Integrative Biology, Oklahoma State University, Stillwater, Oklahoma, United States.
To maintain internal ion balance in marine environments, teleost fishes leverage seawater (SW)-type ionocytes to actively secrete Na and Cl into the environment. It is well established that SW-type ionocytes use apically expressed cystic fibrosis transmembrane conductance regulator 1 (Cftr1) as a conduit for Cl to exit the gill. Here, we investigated whether the Ca-activated Cl channel, anoctamin 1 (Ano1), provides an additional path for Cl-secretion in euryhaline mummichogs ().
View Article and Find Full Text PDFCell Tissue Res
August 2024
Laboratory of Physiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, 277-8564, Japan.
In teleost fish, branchial ionocytes are important sites for osmoregulation and acid-base regulation by maintaining ionic balance in the body fluid. During the early developmental stages before the formation of the gills, teleost ionocytes are localized in the yolk-sac membrane and body skin. By comparing with teleost fish, much less is known about ionocytes in developing embryos of elasmobranch fish.
View Article and Find Full Text PDFJ Comp Physiol B
October 2024
Department of Integrative Biology, Oklahoma State University, 501 Life Sciences West, Stillwater, OK, 74078, USA.
The endocrine system is an essential regulator of the osmoregulatory organs that enable euryhaline fishes to maintain hydromineral balance in a broad range of environmental salinities. Because branchial ionocytes are the primary site for the active exchange of Na, Cl, and Ca with the external environment, their functional regulation is inextricably linked with adaptive responses to changes in salinity. Here, we review the molecular-level processes that connect osmoregulatory hormones with branchial ion transport.
View Article and Find Full Text PDFZoolog Sci
February 2024
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan,
Vertebrates have expanded their habitats during evolution, which accompanies diversified routes for water acquisition. Water is acquired by oral intake and subsequent absorption by the intestine in terrestrial and marine animals which are subjected to constant dehydration, whereas most water is gained osmotically across body surfaces in freshwater animals. In addition, a significant amount of water, called metabolic water, is produced within the body by the oxidation of hydrogen in organic substrates.
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