Interactions between cortisol and Rhesus glycoprotein expression in ureogenic toadfish, Opsanus beta

Tamara M. Rodela, M. Danielle McDonald, Patrick J. Walsh, Kathleen M. Gilmour

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

In their native environment, gulf toadfish excrete equal quantities of ammonia and urea. However, upon exposure to stressful conditions in the laboratory (i.e. crowding, confinement or air exposure), toadfish decrease branchial ammonia excretion and become ureotelic. The objective of this study was to determine the influences of Cortisol and ammonia on ammonia excretion relative to expression of Rhesus (Rh) glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). In vivo infusions and/or injections were used to manipulate corticosteroid activity and plasma ammonia concentrations in ureotelic toadfish. Metyrapone treatment to lower circulating Cortisol levels resulted in a 3.5-fold elevation of ammonia excretion rates, enhanced mRNA expression of two of the toadfish Rh isoforms (Rhcgl and Rhcg2), and decreased branchial and hepatic GS activity. Correspondingly, Cortisol infusion decreased ammonia excretion 2.5-fold, a change that was accompanied by reduced branchial expression of all toadfish Rh isoforms (Rhag, Rhbg, Rhcgl and Rhcg2) and a twofold increase in hepatic GS activity. In contrast, maintenance of high circulating ammonia levels by ammonia infusion enhanced ammonia excretion and Rh expression (Rhag, Rhbg and Rhcg2). Toadfish treated with Cortisol showed an attenuated response to ammonia infusion with no change in Rh mRNA expression or GS activity. In summary, the evidence suggests that ammonia excretion in toadfish is modulated by cortisolinduced changes in both Rh glycoprotein expression and GS activity.

Original languageEnglish (US)
Pages (from-to)314-323
Number of pages10
JournalJournal of Experimental Biology
Volume215
Issue number2
DOIs
StatePublished - Jan 2012

Keywords

  • Ammonia
  • Cortisol
  • Gill
  • Glutamine synthetase
  • Gulf toadfish
  • Nitrogen excretion
  • Opsanus beta
  • Plasma
  • Rhesus proteins
  • Urea

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Physiology
  • Insect Science
  • Aquatic Science

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