TY - JOUR
T1 - Characterization of Na+ uptake in the endangered desert pupfish, Cyprinodon macularius (Baird and Girard)
AU - Brix, Kevin V.
AU - Grosell, Martin
N1 - Funding Information:
Cyprinodon macularius were generously provided by Chris Ingersoll at the USGS Laboratory in Columbia, MO, USA and held under USFWS Endangered Species Permit #TE2057312. Experiments were approved by the University of Miami animal care committee. This work was supported by a University of Miami Maytag Fellowship (to KVB), a National Science Foundation Graduate Research Fellowship (to KVB), and the National Science Foundation (IOB 0743903 and IOS 1146695 to MG).
Publisher Copyright:
© The Author 2013.
PY - 2013
Y1 - 2013
N2 - This study provided an initial characterization of Na+ uptake in saline freshwater by the endangered pupfish, Cyprinodon macularius. This species occurs only in several saline water systems in the southwestern USA and northern Mexico, where salinity is largely controlled by water-management practices. Consequently, understanding the osmoregulatory capacity of this species is important for their conservation. The lower acclimation limit of C. macularius in freshwater was found to be 2 mM Na+. Fish acclimated to 2 or 7 mM Na+ displayed similar Na+ uptake kinetics, with Km values of 4321 and 3672 μM and Vmax values of 4771 and 3602 nmol g-1 h-1, respectively. A series of experiments using pharmacological inhibitors indicated that Na+ uptake in C. macularius was not sensitive to bumetanide, metolazone, or phenamil. These results indicate the Na+- K+-2Cl- cotransporter, Na+-Cl- cotransporter, and the Na+ channel-H+-ATPase system are likely not to be involved in Na+ uptake at the apical membrane of fish gill ionocytes in fish acclimated to 2 or 7 mM Na+. However, Na+ uptake was sensitive to 1 × 10-3 M amiloride (not 1 × 10-4 or 1 × 10-5 M), 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), and ethoxzolamide. These data suggest that C. macularius relies on a low-affinity Na+-H+ exchanger for apical Na+ uptake and that H+ ions generated via carbonic anhydrase-mediated CO2 hydration are important for the function of this protein.
AB - This study provided an initial characterization of Na+ uptake in saline freshwater by the endangered pupfish, Cyprinodon macularius. This species occurs only in several saline water systems in the southwestern USA and northern Mexico, where salinity is largely controlled by water-management practices. Consequently, understanding the osmoregulatory capacity of this species is important for their conservation. The lower acclimation limit of C. macularius in freshwater was found to be 2 mM Na+. Fish acclimated to 2 or 7 mM Na+ displayed similar Na+ uptake kinetics, with Km values of 4321 and 3672 μM and Vmax values of 4771 and 3602 nmol g-1 h-1, respectively. A series of experiments using pharmacological inhibitors indicated that Na+ uptake in C. macularius was not sensitive to bumetanide, metolazone, or phenamil. These results indicate the Na+- K+-2Cl- cotransporter, Na+-Cl- cotransporter, and the Na+ channel-H+-ATPase system are likely not to be involved in Na+ uptake at the apical membrane of fish gill ionocytes in fish acclimated to 2 or 7 mM Na+. However, Na+ uptake was sensitive to 1 × 10-3 M amiloride (not 1 × 10-4 or 1 × 10-5 M), 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), and ethoxzolamide. These data suggest that C. macularius relies on a low-affinity Na+-H+ exchanger for apical Na+ uptake and that H+ ions generated via carbonic anhydrase-mediated CO2 hydration are important for the function of this protein.
KW - Carbonic anhydrase
KW - Cyprinodon macularius
KW - Na-H exchanger
KW - Osmoregulation
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U2 - 10.1093/conphys/cot005
DO - 10.1093/conphys/cot005
M3 - Article
AN - SCOPUS:84983526993
VL - 1
JO - Conservation Physiology
JF - Conservation Physiology
SN - 2051-1434
IS - 1
M1 - cot005
ER -