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ZFIN ID: ZDB-PUB-081001-2
Ammonia excretion by the skin of zebrafish (Danio rerio) larvae
Shih, T.H., Horng, J.L., Hwang, P.P., and Lin, L.Y.
Date: 2008
Source: American journal of physiology. Cell physiology   295(6): C1625-C1632 (Journal)
Registered Authors: Horng, Jiun-Lin, Hwang, Pung Pung
Keywords: zebrafish, ammonia, H+-ATPase, ionocytes, Rh glycoprotein
MeSH Terms:
  • Ammonia/metabolism*
  • Animals
  • Cation Transport Proteins/metabolism
  • H(+)-K(+)-Exchanging ATPase/metabolism
  • Ion-Selective Electrodes
  • Larva
  • Proton Pumps/metabolism
  • Skin/metabolism*
  • Zebrafish/physiology*
  • Zebrafish Proteins/metabolism
PubMed: 18815227 Full text @ Am. J. Physiol. Cell Physiol.
The mechanism of ammonia excretion in freshwater teleosts is not well understood. In this study, scanning ion-selective electrode technique (SIET) 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 (HRCs), which were identified as the H(+)-secreting ionocyte in zebrafish. Minor NH4(+) 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 NH4(+) 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-oligoneculeotides also decreased NH4(+) excretion. This study demonstrates ammonia excretion in epithelial cells of larval skin through an acid-trapping mechanism, and provides direct evidence for the involvement of the H(+) pump and an Rh glycoprotein (Rhcg1) in ammonia excretion. Key words: zebrafish, ammonia, H+-ATPase, ionocytes.