Na+/K+-ATPase and vacuolar-type H+-ATPase in the gills of the aquatic air-breathing fish Trichogaster microlepis in response to salinity variation.
The aquatic air-breathing fish, Trichogaster microlepis, can be found in fresh water and estuaries. We further evaluated the changes in two important osmoregulatory enzymes, Na(+)/K(+)-ATPase (NKA) and vacuolar-type H(+)-ATPase (VHA), in the gills when fish were subjected to deionized water (DW), fresh water (FW), and salinated brackish water (salinity of 10 g/L). Fish were sampled only 4 days after experimental transfer. The mortality, plasma osmolality, and Na(+) concentration were higher in 10 g/L acclimated fish, while their muscle water content decreased with elevated external salinity. The highest NKA protein abundance was found in the fish gills in 10 g/L, and NKA activity was highest in the DW and 10 g/L acclimated fish. The VHA protein levels were highest in 10 g/L, and VHA activity was highest in the DW treatment. From immunohistochemical results, we found three different cell populations: (1) NKA-immunoreactive (NKA-IR) cells, (2) both NKA-IR and HA-IR cells, and (3) HA-IR cells. NKA-IR cells in the lamellar and interlamellar regions significantly increased in DW and 10 g/L treatments. Only HA-IR cells in the lamellar region were significantly increased in DW. In the interlamellar region, there was no difference in the number of HA-IR cells among the three treated. From these results, T. microlepis exhibited osmoregulatory ability in DW and 10 g/L treatments. The cell types involved in ionic regulation were also examined with immunofluorescence staining; three ionocyte types were found which were similar to the zebrafish model.
Huang
Chun-Yen
CY
Department of Life Science, Tunghai University, Taichung 40704, Taiwan.
Chao
Pei-Lin
PL
Lin
Hui-Chen
HC
D000388:Air; D000818:Animals; D029941:Fish Proteins / Q000378:metabolism; D005399:Fishes / Q000097:blood / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D005880:Gills / Q000166:cytology / Q000201:enzymology*; D015151:Immunoblotting; D018613:Microscopy, Confocal; D009132:Muscles / Q000378:metabolism; D009994:Osmolar Concentration; D010101:Oxygen Consumption / Q000502:physiology*; D054712:Salinity; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D016019:Survival Analysis; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*; D014867:Water / Q000378:metabolism
D029941:Fish Proteins; D028021:Sodium-Potassium-Chloride Symporters; D014867:Water; D025262:Vacuolar Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase