title: Responses of gill mitochondria-rich cells in Mozambique tilapia exposed to acidic environments (pH 4.0) in combination with different salinities.
abstract: On exposure to hyposmotic acidic water, teleost fish suffer from decreases in blood osmolality and pH, and consequently activate osmoregulatory and acid-base regulatory mechanisms to restore disturbed ion and acid-base balances. In Mozambique tilapia Oreochromis mossambicus exposed to acidic (pH 4.0) or neutral (pH 7.4-7.7) freshwater in combination with 0mM or 50mM NaCl, we examined functional and morphological changes in gill mitochondria-rich (MR) cells. We assessed gene expression of Na(+)/H(+) exchanger-3 (NHE3), Na(+)/Cl(-) cotransporter (NCC), vacuolar-type H(+)-ATPase (V-ATPase) and Na(+)/HCO(3)(-) cotransporter-1 (NBC1) in the gills. The mRNA expression of NHE3 and NCC in tilapia gills were higher in acidic freshwater than in that supplemented with 50mM NaCl, while there was no significant difference in mRNA levels of V-ATPase and NBC1. In addition, immunocytochemical observations showed that apical-NHE3 MR cells were enlarged, and frequently formed multicellular complexes with developed deep apical openings in acidic freshwater with 0mM and 50mM NaCl. These findings suggest that gill MR cells respond to external salinity and pH treatments, by parallel manipulation of osmoregulatory and acid-base regulatory mechanisms.
authors.affiliation: Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan. fumiya@marine.fs.a.u-tokyo.ac.jp
authors.forename: Fumiya
authors.initials: F
authors.lastname: Furukawa
authors.forename: Soichi
authors.initials: S
authors.lastname: Watanabe
authors.forename: Mayu
authors.initials: M
authors.lastname: Inokuchi
authors.forename: Toyoji
authors.initials: T
authors.lastname: Kaneko
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002712:Chlorides / Q000097:blood; D029941:Fish Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005880:Gills / Q000166:cytology / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D016623:Ion Pumps / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D012333:RNA, Messenger / Q000378:metabolism; D054712:Salinity; D012964:Sodium / Q000097:blood; D027982:Sodium-Bicarbonate Symporters / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D017210:Tilapia / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D002712:Chlorides; D029941:Fish Proteins; D016623:Ion Pumps; D012333:RNA, Messenger; D027982:Sodium-Bicarbonate Symporters; D012964:Sodium