An ionocyte (formerly called a chloride cell) is a mitochondrion-richcell within ionoregulatory organs of animals, such as teleostfish gill, insect Malpighian tubules, crustacean gills, antennal glands and maxillary glands, and copepod Crusalis organs.[1] These cells contribute to the maintenance of optimal osmotic, ionic, and acid-base levels within metazoans. In aquatic invertebrates, ionocytes perform the functions of both ion uptake and ion excretion.[2] In marine teleost fish, by expending energy to power the enzyme Na+/K+-ATPase and in coordination with other protein transporters, ionocytes pump excessive sodium and chlorideions against the concentration gradient into the ocean.[3][4][5] Conversely, freshwater teleost ionocytes use this low intracellular environment to attain sodium and chloride ions into the organism, and also against the concentration gradient.[3][5] In larval fishes with underdeveloped / developing gills, ionocytes can be found on the skin and fins.[6][7][8]
Marine teleost fishes consume large quantities of seawater to reduce osmotic dehydration.[9] The excess of ions absorbed from seawater is pumped out of the teleost fishes via the ionocytes.[9] These cells use active transport on the basolateral (internal) surface to accumulate chloride, which then diffuses out of the apical (external) surface and into the surrounding environment.[10] Such mitochondrion-rich cells are found in both the gill lamellae and filaments of teleost fish. Using a similar mechanism, freshwater teleost fish use these cells to take in salt from their dilute environment to prevent hyponatremia from water diffusing into the fish.[10] In the context of freshwater fish, ionocytes are often referred to as "mitochondria-rich cells", to emphasis their high density of mitochondria.[11]
See also
Pulmonary ionocyte - a rare type of specialised cell that may regulate mucus viscosity in humans
↑Fernandes, M.N. (2019) "Respiration and Ionic-Osmoregulation". In: Formicki K and Kirschbaum F (Eds.) The Histology of Fishes pages 246–266, CRC Press. Шаблон:ISBN.
