Identification of α-adrenergic receptors in human platelets by [3H]dihydroergocryptine binding

K. D. Newman, L. T. Williams, Nanette Bishopric, R. J. Lefkowitz

Research output: Contribution to journalArticle

122 Citations (Scopus)

Abstract

Binding of [3H]dihydroergocryptine to platelet lysates appears to have all the characteristics of binding to α-adrenergic receptors. At 25°C binding reaches equilibrium within 20 min and is reversible upon addition of excess phentolamine. Binding is saturable with 183±22 fmol of [3H]dihydroergocryptine bound per mg of protein at saturation, corresponding to 220±26 sites per platelet. Kinetic and equilibrium studies indicate the dissociation constant of [3H]dihydroergocryptine for the receptors is 1-3 nM. The specificity of the binding sites is typical of an α-adrenergic receptor. Catecholamine agonists compete for occupancy of the [3H]dihydroergocryptine binding sites with an order of potency (-)epinephrine > (-)norepinephrine >> (-)isoproterenol. Stereospecificity was demonstrated inasmuch as the (+)isomers of epinephrine and norepinephrine were 10-20-fold less potent than the (-)isomers. The potent α-adrenergic antagonists phentolamine, phenoxybenzamine, and yohimbine competed potently for the sites, whereas β-antagonists such as propranolol and dichlorisoproterenol were quite weak. Dopamine and serotonin competed only at high concentrations (0.1 mM). The [3H]dihydroergocryptine binding sites could also be demonstrated in intact platelets where they displayed comparable specificity, stereospecificity, and saturability. Saturation binding studies with the intact platelets indicated 220±45 receptors per platelet, in good agreement with the value derived from studies with platelet lysates. Ability of α-adrenergic agonists to inhibit adenylate cyclase and of α-adrenergic antagonists to antagonize this inhibitory effect directly paralleled ability to interact with the [3H]dihydroergocryptine binding sites. These data demonstrate the feasibility of directly studying α-adrenergic receptor binding sites in human platelets with [3H]dihydroergocryptine.

Original languageEnglish
Pages (from-to)395-402
Number of pages8
JournalJournal of Clinical Investigation
Volume61
Issue number2
StatePublished - Jan 1 1978
Externally publishedYes

Fingerprint

Dihydroergocryptine
Adrenergic Receptors
Blood Platelets
Binding Sites
Adrenergic Antagonists
Phentolamine
Epinephrine
Norepinephrine
Phenoxybenzamine
Adrenergic Agonists
Yohimbine
Isoproterenol
Adenylyl Cyclases
Propranolol
Catecholamines
Dopamine
Serotonin

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Newman, K. D., Williams, L. T., Bishopric, N., & Lefkowitz, R. J. (1978). Identification of α-adrenergic receptors in human platelets by [3H]dihydroergocryptine binding. Journal of Clinical Investigation, 61(2), 395-402.

Identification of α-adrenergic receptors in human platelets by [3H]dihydroergocryptine binding. / Newman, K. D.; Williams, L. T.; Bishopric, Nanette; Lefkowitz, R. J.

In: Journal of Clinical Investigation, Vol. 61, No. 2, 01.01.1978, p. 395-402.

Research output: Contribution to journalArticle

Newman, KD, Williams, LT, Bishopric, N & Lefkowitz, RJ 1978, 'Identification of α-adrenergic receptors in human platelets by [3H]dihydroergocryptine binding', Journal of Clinical Investigation, vol. 61, no. 2, pp. 395-402.
Newman, K. D. ; Williams, L. T. ; Bishopric, Nanette ; Lefkowitz, R. J. / Identification of α-adrenergic receptors in human platelets by [3H]dihydroergocryptine binding. In: Journal of Clinical Investigation. 1978 ; Vol. 61, No. 2. pp. 395-402.
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