Agonist versus antagonist binding to alpha-adrenergic receptors.

Published

Journal Article

The binding properties of two alpha-adrenergic radioligands, [3H]epinephrine (an agonist) and [3H]dihydroergocryptine (an antagonist), were compared in two model systems--membranes derived from human platelets and membranes from rat liver. The platelet contains exclusively alpha 2 and the liver mostly (approximately 80%) alpha 1 receptors. Agonists induce the formation of a guanine nucleotide-sensitive high-affinity state of alpha 2 but not alpha 1 receptors. [3H]Dihydroergocryptine labels all the alpha receptors, whereas [3H]epinephrine at low concentrations labels predominantly the high-affinity form of the alpha 2 receptor in both platelet and liver. However, in the liver, alpha-adrenergic effects such as glycogen phosphorylase activation are shown to be mediated via alpha 1 receptors. Thus, in liver membranes the endogenous "physiological" agonist may not label the physiologically relevant alpha 1 receptors in typical radioligand binding assays using low concentrations of [3H]epinephrine.

Full Text

Duke Authors

Cited Authors

  • Hoffman, BB; Michel, T; Kilpatrick, DM; Lefkowitz, RJ; Tolbert, ME; Gilman, H; Fain, JN

Published Date

  • August 1, 1980

Published In

Volume / Issue

  • 77 / 8

Start / End Page

  • 4569 - 4573

PubMed ID

  • 6107908

Pubmed Central ID

  • 6107908

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.77.8.4569

Language

  • eng

Conference Location

  • United States