Angiotensin signaling and receptor types in teleost fish

M. J. Russell, A. M. Klemmer, K. R. Olson

Research output: Contribution to journalReview article

38 Scopus citations

Abstract

Despite advances characterizing mammalian angiotensin receptors, the phylogeny of fish angiotensin receptors remains unclear. Three aspects of receptor function: (1) the nature of the ligand; (2) the second messenger system activated by it; and (3) the pharmacological profile of specific antagonists, are examined to provide insight into the fish receptor. (1) The octapeptide sequences of fish and mammalian angiotensin II (ANG II) are nearly homologous, differing only at the first and fifth residues. Both peptides are almost equally efficacious and equipotent in heterologous systems and both contain key agonist switches Tyr4 and Phe8 necessary to activate mammalian AT1-type receptors. (2) ANG II increases inositol trisphosphate production, and elevates intracellular calcium in fish tissues consistent with activation of the AT1 receptor. (3) However, the specific mammalian sartan-type AT1 antagonists, e.g. losartan, produce inconsistent results in fish often acting as partial agonists, or inhibiting only at elevated concentrations. Because sartans and ANG II act at distinct sites on the AT1 receptor, we propose that the teleost receptor is an AT1-type receptor that is fairly well conserved with respect to both the ANG binding site and coupling to the second messenger system, whereas the sartan binding site has been poorly conserved. The evidence for non-AT1 type ANG II receptors in teleosts is limited. Mammalian AT2 receptor antagonists are generally ineffective but may block at elevated, non-specific doses. Truncated ANG II fragments, ANG III and ANG IV, are often less potent than ANG II, however, their receptors have not been examined. Preliminary studies in trout indicate that angiotensin 1-7 may have a mild vasodilatory effect; additional work is needed to determine if non-AT1-type receptors are involved.

Original languageEnglish (US)
Pages (from-to)41-51
Number of pages11
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Volume128
Issue number1
DOIs
StatePublished - Jan 1 2001

Keywords

  • AT receptors
  • Bony fish
  • Gill
  • Intestine
  • Kidney
  • Liver
  • Renin-angiotensin system
  • Vascular smooth muscle

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Molecular Biology

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