Acute exposure to waterborne copper inhibits both the excretion and uptake of ammonia in freshwater rainbow trout (Oncorhynchus mykiss)

Michael Yu Ting Lim, Alex M. Zimmer, Chris M. Wood

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

In freshwater fish, exposure to sub-lethal concentrations of waterborne copper (Cu) results in inhibitions of ammonia excretion (Jamm) and Na+ uptake (JNa in), yet the mechanisms by which these occur are not fully understood. In the present study, rainbow trout (Oncorhynchus mykiss) fry exposed to 50 μg/l Cu for 24 h displayed a sustained 40% decrease in Jamm and a transient 60% decrease in JNa in. Previously, these effects have been attributed to inhibitions of gill Na+/K+-ATPase and/or carbonic anhydrase (CA) activities by Cu. Trout fry did not display significant reductions in the branchial activities of these enzymes or H+-ATPase over 24 h Cu exposure. Recently, Rhesus (Rh) glycoproteins, bi-directional NH3 gas channels, have been implicated in the mechanismof Cu toxicity. Juvenile trout were exposed to nominal 0, 50, and 200 μg/l Cu for 3-6 h under control conditions (ammonia-free water) followed by 6 h exposure to high environmental ammonia (HEA; 1.5 mmol/l NH4HCO3). HEA led to significant ammonia uptake in control fish (0 μg/l Cu), and exposure to 50 and 200 μg/l Cu resulted in significant reductions of ammonia uptake during HEA exposure. This is the first evidence that Cu inhibits both the excretion and uptake of ammonia, implicating bi-directional Rh glycoproteins as a target for Cu toxicity. We propose a model whereby Rh blockade by Cu causes the sustained inhibition of Jamm and transient inhibition of JNa in, with H+-ATPase potentially aiding in JNa in recovery. More work is needed to elucidate the role of Rh proteins in sub-lethal Cu toxicity.

Original languageEnglish (US)
Pages (from-to)48-54
Number of pages7
JournalComparative Biochemistry and Physiology Part - C: Toxicology and Pharmacology
Volume168
DOIs
StatePublished - Feb 2015

Keywords

  • Ammonia excretion (J)
  • Carbonic anhydrase (CA)
  • Copper
  • H-ATPase
  • High environmental ammonia (HEA)
  • Na/K-ATPase
  • Rhesus (Rh) glycoproteins
  • Sodium uptake (J )

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Physiology
  • Health, Toxicology and Mutagenesis
  • Toxicology

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