Rhcg1 and NHE3b are involved in ammonium-dependent sodium uptake by zebrafish larvae acclimated to low-sodium water
- Authors
- Shih, T.H., Horng, J.L., Liu, S.T., Hwang, P.P., and Lin, L.Y.
- ID
- ZDB-PUB-111027-2
- Date
- 2012
- Source
- American journal of physiology. Regulatory, integrative and comparative physiology 302(1): R84-93 (Journal)
- Registered Authors
- Horng, Jiun-Lin, Hwang, Pung Pung
- Keywords
- zebrafish, fish, gill, skin, embryo
- MeSH Terms
-
- Acclimatization/physiology*
- Acid-Base Equilibrium/physiology
- Animals
- Biological Transport/physiology
- Cation Transport Proteins/genetics
- Cation Transport Proteins/metabolism*
- Embryo, Nonmammalian/metabolism*
- Gene Knockdown Techniques
- Ion-Selective Electrodes
- Models, Animal
- Quaternary Ammonium Compounds/metabolism*
- Salinity*
- Sodium/metabolism*
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/metabolism*
- Water-Electrolyte Balance/physiology
- Yolk Sac/metabolism
- Zebrafish/metabolism*
- Zebrafish Proteins/genetics
- Zebrafish Proteins/metabolism*
- PubMed
- 21993530 Full text @ Am. J. Physiol. Regul. Integr. Comp. Physiol.
To investigate whether Na+ uptake by zebrafish is dependent on NH4+ excretion, a scanning ion-selective electrode technique (SIET) was applied to measure Na+ and NH4+ gradients at the yolk-sac surface of zebrafish larvae. Low-Na+ acclimation induced an inward Na+ gradient (uptake), and a combination of low-Na+ and high-NH4+ induced a larger inward Na+ gradient. When measuring the ionic gradients, raising the external NH4+ level (5 mM) simultaneously blocked NH4+ excretion and Na+ uptake; in contrast, raising the external Na+ level (10 mM) simultaneously enhanced Na+ uptake and NH4+ excretion. The addition of MOPS buffer (5 mM) which is known to block NH4+ excretion also suppressed Na+ uptake. These results showed that Na+ uptake and NH4+ excretion by larval skin are associated when ambient Na+ level is low. Knockdown of Rhcg1 translation with morpholino-oligonucleotides decreased both NH4+ excretion and Na+ uptake by the skin and Na+ content of whole larvae. Knockdown of nhe3b translation or inhibitor (EIPA) treatment also decreased both the NH4+ excretion and Na+ uptake. This study provides loss-of-function evidence for the involvement of Rhcg1 and NHE3b in the ammonium-dependent Na+ uptake mechanism in zebrafish larvae subjected to low-Na+ water.