title: Osmoregulation in zebrafish: ion transport mechanisms and functional regulation.
abstract: Fish, like mammals, have to maintain their body fluid ionic and osmotic homeostasis through sophisticated iono-/osmoregulation mechanisms, which are conducted mainly by ionocytes of the gill (the skin in embryonic stages), instead of the renal tubular cells in mammals. Given the advantages in terms of genetic database availability and manipulation, zebrafish is an emerging model for research into regulatory and integrative physiology. At least five types of ionocytes, HR, NaR, NCC, SLC26, and KS cells, have been identified to carry out Na(+) uptake/H(+) secretion/NH4 (+) excretion, Ca(2+) uptake, Na(+)/Cl(-) uptake, K(+) secretion, and Cl(-) uptake/HCO3 (-) secretion, respectively, through distinct sets of transporters. Several hormones, namely isotocin, prolactin, cortisol, stanniocalcin-1, calcitonin, endothelin-1, vitamin D, parathyorid hormone 1, catecholamines, and the renin-angiotensin-system, have been demonstrated to positively or negatively regulate ion transport through specific receptors at different ionocytes stages, at either the transcriptional/translational or posttranslational level. The knowledge obtained using zebrafish answered many long-term contentious or unknown issues in the field of fish iono-/osmoregulation. The homology of ion transport pathways and hormone systems also means that the zebrafish model informs studies on mammals or other animal species, thereby providing insights into related fields.
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Nakang, Taipei, Taiwan ; Institute of Biological Chemistry, Academia Sinica, Nakang, Taipei, Taiwan.
authors.forename: Ying-Jey
authors.initials: YJ
authors.lastname: Guh
authors.affiliation: National Institute for Basic Biology, Myodaiji-cho, Okazaki, 444-8787, Japan.
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Institute of Cellular and Organismic Biology, Academia Sinica, Nakang, Taipei, Taiwan.
authors.forename: Pung-Pung
authors.initials: PP
authors.lastname: Hwang
keywords: Osmoregulation; hormone; ion regulation; ionocyte; zebrafish