An endogenous factor induces heterogeneity of binding sites of selective muscarinic receptor antagonists in rat heart

Allison D. Fryer, Esam E. El-Fakahany

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

According to molecular biological and pharmacological criteria, rat heart membranes normally express only one muscarinic receptor subtype. The selective antagonists pirenzepine and AF-DX 116 bind to this receptor with a single affinity: low and high, respectively. We report here that an endogenous, intracellular factor alters the affinity of selective antagonists for muscarinic receptors in the heart. Thus, when the intracellular fluid is added back to rat heart membranes, both pirenzepine and AF-DX 116 bind to two receptor sites. Approximately 30% of the receptors bind pirenzepine with high affinity and AF-DX 116 with low affinity. Thus, while cardiac muscarinic receptors are coded for by a single mRNA and are therefore genetically homogeneous, the resulting receptor protein might behave like a mixture of receptor subtypes in intact tissues due to the influence of intracelluar factors on receptor conformation.

Original languageEnglish (US)
Pages (from-to)127-132
Number of pages6
JournalMolecular Membrane Biology
Volume8
Issue number3
DOIs
StatePublished - Jan 1 1989

Keywords

  • AF-DX 116
  • Ligand binding
  • Muscarinic receptor
  • Pirenzepine
  • Receptor subtypes

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