Abstract
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.
| Original language | English (US) |
|---|---|
| Article number | cot005 |
| Journal | Conservation Physiology |
| Volume | 1 |
| Issue number | 1 |
| DOIs | |
| State | Published - 2013 |
| Externally published | Yes |
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Keywords
- Carbonic anhydrase
- Cyprinodon macularius
- Na-H exchanger
- Osmoregulation
ASJC Scopus subject areas
- Nature and Landscape Conservation
- Management, Monitoring, Policy and Law
- Ecological Modeling
- Physiology
Cite this
Characterization of Na+ uptake in the endangered desert pupfish, Cyprinodon macularius (Baird and Girard). / Brix, Kevin V.; Grosell, Martin.
In: Conservation Physiology, Vol. 1, No. 1, cot005, 2013.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Characterization of Na+ uptake in the endangered desert pupfish, Cyprinodon macularius (Baird and Girard)
AU - Brix, Kevin V.
AU - Grosell, Martin
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
UR - http://www.scopus.com/inward/record.url?scp=84983526993&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84983526993&partnerID=8YFLogxK
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 -