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Effects of environmental sodium ion concentration on the activity of Na/K‐ATPase. H‐ATPase and Glutamate Dehydrogenase from the gills of fathead minnows ( Pimephales promelas )
Author(s) -
Packer Randall K.,
Monroe Ian,
Wentworth Simon A.,
Garvin Jeffrey L.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.lb751
Subject(s) - sodium , atpase , gill , chemistry , glutamate dehydrogenase , pimephales promelas , ion transporter , epithelial polarity , biochemistry , sodium glutamate , ammonium , minnow , enzyme , medicine , biology , glutamate receptor , cell , membrane , fish <actinopterygii> , raw material , receptor , organic chemistry , fishery
Na + /K + ATPase on the basolateral membrane of gill epithelial cells actively transports Na + from the cell interior to the blood, creating the electrochemical gradient that may help drive secondary active transporters in the apical membrane essential for Na + influx. H + ‐ATPase on apical membranes has been hypothesized to facilitate Na + uptake. In the renal proximal tubules of mammals glutamate dehydrogenase, GDH, along with phosphate‐dependent glutaminase, deamminates glutamine. Ammonium ions generated exit the apical cell membrane in exchange for Na + entering the cell via NEH3. We hypothesized that Na/K ATPase, H‐ATPase and GDH activity would be higher in fish acclimated to 1.2 mEq/l [Na + ] versus 124 mEq/l environmental [Na + ]. Fathead minnows were acclimated to 1.2, 3.2 or 124mE/l Na + for a minimum of 28 days. Na/K ATPase, H‐ATPase and GDH activities were measured in homogenates of gill tissue. Na/K‐ATPase activity from fish acclimated to 1.4 mE/l (1.99± 0.19 μEq/g protein·hr −1 ) was significantly (P<0.05) higher than in fish acclimatized to 124 mEq/l (1.41±1.34 μEq/g protein·hr −1 ). Similarly, GDH activity increased significantly, from 12.32±1.59 to 24.81±2.54 nanoEq/g protein·hr −1 g in fish acclimated to 1.2 mEq/l compared to those acclimated to 124 mQ/l Na + . In contrast, H + ‐ATPase activity was essentially zero (0.1 ± 0.06 μmoles/mg protein/hr) in fish acclimated to 1.2 mEq/l [Na + ] and increased to 0.58±0.10 μmoles/mg protein/hr in fish acclimated to 124 mEq/l [Na + ]. These data do not support a role for H + ATPase in gill Na + uptake at low environmental [Na + ] but do suggest that at low environmental [Na + ] ammonium ions generated from deamination of glutamine might exchange at the apical gill membrane for sodium ions entering the cell via NEH3. Support or Funding Information Supported by the Columbian College of Arts and Sciences, GWU