Metabolic fate of exogenous 15NH4Cl in the gulf toadfish (Opsanus beta)

Lenore P. Rodicio, Leonel Da Silveira Lobo Sternberg, Patrick J. Walsh

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


This study was undertaken to determine whether gulf toadfish (Opsanus beta) could metabolize ammonia from their environment into other, less toxic products. To this end, gulf toadfish were exposed to 3.8 mM 15NH 4Cl in seawater for 24 and 48 h. Liver, kidney, gill, brain and muscle samples were analyzed for distribution of 15N within the tissue and among various nitrogen-containing metabolites (ammonia, amino-N, glutamine-N, urea and protein). The data reported here show that the toadfish can indeed take up and metabolize ammonia. Analysis of individual metabolic products of ammonia indicates that the toadfish can convert this toxic chemical into other less toxic metabolites. Ammonia enrichment is significantly different over controls in the kidney, brain and muscle. Urea enrichment is most significant in the brain, with less significant enrichment occurring in the liver and muscle. While accumulation of ammonia into an amino acid pool was not a significant metabolic fate, protein synthesis was significantly enriched in all tissues (with the highest levels occurring in the gill) indicating that amino acid synthesis may be a pathway of ammonia detoxification en route to protein synthesis, and that environmental ammonia can be 'fixed' into protein. Finally, it was found that glutamine-N synthesis occurs at significant levels in the liver, brain and muscle.

Original languageEnglish (US)
Pages (from-to)157-164
Number of pages8
JournalComparative Biochemistry and Physiology - C Toxicology and Pharmacology
Issue number2
StatePublished - Oct 1 2003
Externally publishedYes


  • NHCl
  • Gulf toadfish
  • Hepatic encephalopathy
  • Hyperammonemia
  • Opsanus beta
  • Ornithine-urea cycle

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Health, Toxicology and Mutagenesis
  • Pharmacology


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