Activity of the unique beta-adrenergic Na+/H+ exchanger in trout erythrocytes is controlled by a novel beta3-AR subtype

Am J Physiol Regul Integr Comp Physiol. 2003 Sep;285(3):R526-35. doi: 10.1152/ajpregu.00146.2003. Epub 2003 May 29.


beta-Adrenoceptors (beta-ARs) are seven-transmembrane domain, G protein-coupled receptors that transduce the cellular effects of epinephrine and norepinephrine and play a pivotal role in the vertebrate stress response. This study reports the cloning and characterization of two previously unreported beta-ARs from the rainbow trout (Oncorhynchus mykiss). Phylogenetic analysis of amino acid sequences indicates that both beta-ARs are homologs of the mammalian beta3-AR. Analysis of tissue expression patterns indicates that one of these trout beta3-adrenoceptors (beta3a-AR) is highly expressed in gill and heart, whereas the second (beta3b-AR) is highly expressed by red blood cells (RBC). Expression of the beta3b-AR in the RBC coupled with the finding of a single category of beta-AR binding sites on RBC membranes provides strong evidence for the control of the trout RBC beta-AR Na+/H+ exchanger (beta-NHE) activity by signaling through this beta3b-subtype and not through a beta1-subtype as previously proposed. The RBC-specific trout beta3b-AR exhibits binding characteristics that distinguish this receptor from each of the three pharmacologically defined categories of mammalian beta-ARs (beta1-, beta2-, and beta3-AR). This study is the first to report the presence of a beta3-AR subtype in a fish species, and the proposal that the beta3b-AR controls RBC beta-NHE activity represents a novel role for the beta3-AR subtype in vertebrates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Body Temperature Regulation / physiology
  • Erythrocytes / metabolism
  • Evolution, Molecular
  • Molecular Sequence Data
  • Oncorhynchus mykiss / genetics*
  • Phylogeny
  • Receptors, Adrenergic, beta-3 / genetics*
  • Receptors, Adrenergic, beta-3 / metabolism*
  • Signal Transduction / genetics
  • Sodium-Hydrogen Exchangers / genetics*
  • Sodium-Hydrogen Exchangers / metabolism*


  • Receptors, Adrenergic, beta-3
  • Sodium-Hydrogen Exchangers