Expression of three α2-adrenergic receptor subtypes in rat tissues: Implications for α2 receptor classification

W. Lorenz, J. W. Lomasney, S. Collins, J. W. Regan, M. G. Caron, R. J. Lefkowitz

Research output: Contribution to journalArticlepeer-review

159 Scopus citations

Abstract

Based on biochemical and ligand binding studies in various tissues and species, evidence for several α2-adrenergic receptor subtypes has accumulated. The current α2-adrenergic receptor classification (α2A, α2B, α2C) is based exclusively on pharmacological criteria. The molecular cloning of three distinct genes for human α2-adrenergic receptors has confirmed the existence of multiple α2-adrenergic receptor subtypes. According to their localization on different human chromosomes, the receptor genes were termed α2-C10, α2-C4, and α2-C2. The relationship, however, between the pharmacologically characterized α2-adrenergic receptors and the isolated genes has yet to be clarified. Using Northern blot hybridization, we analyzed the expression of the three cloned α2-adrenergic receptor genes in 13 rat tissues, as well as in cell lines previously described as model systems for the pharmacologically defined α2-adrenergic receptor subtypes. The α2-C10 receptor corresponds to the α2A subtype and is expressed in rat brainstem, cerebral cortex, hippo-campus, pituitary gland, cerebellum, kidney, aorta, skeletal muscle, spleen, and lung. Messenger RNA coding for the α2-C4 receptor was detected only in brain regions, not in peripheral tissues, whereas the α2-C2 message was found only in liver and kidney. Hybridization experiments with RNA derived from tissues and cells from which the pharmacological α2-receptor classification has been developed lead to the conclusion that the α2B subtype represents two distinct receptor molecules, the α2-C4 and a subtype previously undetected by classical ligand binding approaches. Furthermore, our results suggest that the α2C subtype characterized in opossum kidney cells is an interspecies variation of α2-C4 rather than a separate subtype. Finally, the cloned α2-C2 receptor was found to be "α2B-like" and not covered by the current pharmacological classification.

Original languageEnglish (US)
Pages (from-to)599-603
Number of pages5
JournalMolecular pharmacology
Volume38
Issue number5
StatePublished - Nov 1990

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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