Time-course changes in the expression of Na+, K+-ATPase in gills and pyloric caeca of brown trout (Salmo trutta) during acclimation to seawater.
Changes in protein and mRNA expression of Na(+),K(+)-ATPase in gills and pyloric caeca of brown trout were investigated on a detailed time course after transfer from freshwater to 25 ppt seawater (SW). A transient deflection in plasma osmolality and muscle water content lasting from 4 h until day 3 was followed by restoration of hydromineral balance from day 5 onward. Gills and pyloric caeca responded to SW transfer by increasing Na(+),K(+)-ATPase activity from days 5 and 3, respectively, onward. In both tissues, this response was preceded by an increase in alpha-subunit Na(+), K(+)-ATPase mRNA as early as 12 h posttransfer. The similarity of the response in these two organs suggests that they both play significant physiological roles in restoring hydromineral balance after abrupt increase in salinity. Further, SW transfer induced a slight, though significant, increase in primary gill filament Na(+), K(+)-ATPase immunoreactive (NKIR) cell abundance. This was paralleled by a marked (50%) decrease in secondary lamellar NKIR cell abundance after less than 1 d in SW. Thus, SW acclimation in brown trout is characterised by a lasting decrease in overall NKIR cell abundance in the gill. We propose that SW transfer stimulates Na(+),K(+)-ATPase enzymatic activity within individual chloride cells long before (<1 d) it becomes apparent in measurements of whole-gill homogenate enzymatic activity. This is supported by the early stabilisation (12 h) of hydromineral balance.
Seidelin
M
M
Institute of Biology, University of Southern Denmark-Main Campus, Odense University, Campusvej 55, DK-5230 Odense M, Denmark.
Madsen
S S
SS
Blenstrup
H
H
Tipsmark
C K
CK
D000818:Animals; D001834:Body Water / Q000378:metabolism; D005260:Female; D005880:Gills / Q000201:enzymology*; D008297:Male; D009132:Muscles / Q000378:metabolism; D011708:Pylorus / Q000201:enzymology*; D012333:RNA, Messenger / Q000378:metabolism; D012474:Salmon / Q000097:blood / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase; D014882:Water-Electrolyte Balance
D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase