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Abstract
The widespread use of beta-adrenoceptor antagonists againist hypertension, angina
pectoris and migraine or as a preventive treatment after myocardial infarction has
encouraged us to investigate the effects of these drugs on platelet function. The
aim of this study was to examine whether beta-blocking drugs interfere with platelet
beta- adrenoceptors and whether this dependency is related to their selectivity for
beta-adrenoceptor subtypes. Beta-adrenoceptor stimulation of human platelets with
isoprenaline increased cyclic AMP (cAMP), which is known to inhibit platelet aggregation.
Furthermore, our studies showed that cAMP formation
was stimulated by non-selective and beta2-selective agonists, but not by the predominant beta-agonist prenalterol. Isoprenaline-
stimulated cAMP formation was blocked by the non- selective beta-adrenoceptor antagonists
propranolol, timolol, and alprenolol, while the betal-selective antagonists atenolol
and metoprolol had no influence on an isoprenaline-induced cAMP formation. Receptor
binding studies using (3H-dyhydroalprenolol revealed an IC50 value for propranolol of 85 nM, while metoprolol only displaced the bound (33H)-dihydroalprenolol at far higher concentrations (IC50, 20 μM). We conclude that the human platelet beta-adrenoceptors are mainly of the
beta2 - subtype and that beta-adrenoceptor antagonists, especially the non-selective antagonists
interfere with platelet function assessed as platelet cAMP formation.

Keywords
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Article info
Publication history
Accepted:
July 2,
1985
Received:
December 27,
1984
Identification
Copyright
© 1985 Published by Elsevier Inc.