PMID: 6107908Aug 1, 1980Paper

Agonist versus antagonist binding to alpha-adrenergic receptors

Proceedings of the National Academy of Sciences of the United States of America
B B HoffmanJ N Fain

Abstract

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.

References

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Citations

Dec 1, 1982·Naunyn-Schmiedeberg's Archives of Pharmacology·B RouotJ Schwartz
Dec 17, 1981·European Journal of Pharmacology·B D Perry, D C U'Prichard
Jul 10, 1981·European Journal of Pharmacology·S Corvera, J A García-Sáinz
Feb 5, 1985·European Journal of Pharmacology·R CashY Agid
Oct 7, 1986·European Journal of Pharmacology·D P Geraghty, E Burcher
Jan 1, 1986·Mechanisms of Ageing and Development·A TsujimotoB B Hoffman
Jan 1, 1983·Pharmacology & Therapeutics·W M TaylorF L Bygrave
Dec 30, 1981·Biochimica Et Biophysica Acta·J R WilliamsonJ B Hoek
Jun 4, 1999·Progress in Biophysics and Molecular Biology·C M SmithS S Taylor
Jul 1, 1982·The New England Journal of Medicine·H J Motulsky, P A Insel
Jul 1, 1981·Proceedings of the National Academy of Sciences of the United States of America·S K Smith, L E Limbird
Dec 1, 1982·Proceedings of the National Academy of Sciences of the United States of America·J W ReganJ P Hieble
Jul 1, 1984·Proceedings of the National Academy of Sciences of the United States of America·N G MorganJ H Exton
Nov 1, 1984·Biological Reviews of the Cambridge Philosophical Society·P H ReinhartF L Bygrave

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