Characterization of the β‐Adrenergic Receptor on the Human Platelet: A β2‐Subtype

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Abstract
The human platelet .beta.-adrenergic receptor was characterized by using the ability of different drugs to stimulate the adenylate cyclase activity and the effects of various .beta.-antagonists to block the isoprenaline-stimulated adenylate cyclase activity. Isoprenaline was 10 times more potent than adrenaline [epinephrine] and 1000 times more potent than noradrenaline [norepinephrine] in stimulating the adenylate cyclase activity in these cells. Isoprenaline-stimulated activity was blocked by the non-selective .beta.-antagonists propranolol and alprenolol and by the .beta.2-selective antagonist IPS 339 [(tert-butyl-amino-3-ol-2-propyl)oximino-9 fluorene] and prenalterol. Metoprolol, a .beta.1-selective blocker, was without effect on the isoprenaline-stimulated adenylate cyclase activity. The .beta.-adrenergic receptor type on the human platelet is evidently mainly of the .beta.2-subtype.