Rhcg1 and NHE3b are involved in ammonium-dependent sodium uptake by zebrafish larvae acclimated to low-sodium water

Am J Physiol Regul Integr Comp Physiol. 2012 Jan 1;302(1):R84-93. doi: 10.1152/ajpregu.00318.2011. Epub 2011 Oct 12.


To investigate whether Na(+) uptake by zebrafish is dependent on NH4(+) excretion, a scanning ion-selective electrode technique 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) 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 (5-ethylisopropyl amiloride) 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.

Publication types

  • Research Support, Non-U.S. Gov't

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 Exchanger 3
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*
  • Water-Electrolyte Balance / physiology
  • Yolk Sac / metabolism
  • Zebrafish / metabolism*
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism*


  • Cation Transport Proteins
  • Quaternary Ammonium Compounds
  • Sodium-Hydrogen Exchanger 3
  • Sodium-Hydrogen Exchangers
  • Zebrafish Proteins
  • rhcgb protein, zebrafish
  • Sodium