Ammonia excretion by the skin of zebrafish (Danio rerio) larvae

Tin Han Shih, Jiun Lin Horng, Pung Pung Hwang, Li Yih Lin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

131 Citations (Scopus)


The mechanism of ammonia excretion in freshwater teleosts is not well understood. In this study, scanning ion-selective electrode technique was applied to measure H+ and NH4+ fluxes in specific cells on the skin of zebrafish larvae. NH4+ extrusion was relatively high in H+ pump-rich cells, which were identified as the H+-secreting ionocyte in zebrafish. Minor NH 4+ extrusion was also detected in keratinocytes and other types of ionocytes in larval skin. NH4+ extrusion from the skin was tightly linked to acid secretion. Increases in the external pH and buffer concentration (5 mM MOPS) diminished H+ and NH 4+ gradients at the larval surface. Moreover, coupled decreases in NH4+ and H+ extrusion were found in larvae treated with an H+-pump inhibitor (bafilomycin A1) or H+-pump gene (atp6v1a) knockdown. Knockdown of Rhcg1 with morpholino-oligonucleotides also decreased NH4+ excretion. This study demonstrates ammonia excretion in epithelial cells of larval skin through an acid-trapping mechanism, and it provides direct evidence for the involvement of the H+ pump and an Rh glycoprotein (Rhcg1) in ammonia excretion.

Original languageEnglish
Pages (from-to)C1625-C1632
JournalAmerican Journal of Physiology - Cell Physiology
Issue number6
Publication statusPublished - 2008 Dec


  • Ammonium
  • H-adenosine 5′-triphosphatase
  • Ion-selective electrode
  • Ionocytes
  • Knockdown
  • Rhesus glycoprotein

ASJC Scopus subject areas

  • Physiology
  • Cell Biology


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