Effects of alpha 2-adrenoceptor agonists and of related compounds on aggregation of, and on adenylate cyclase activity in, human platelets. 1984

K A Clare, and M C Scrutton, and N T Thompson

A range of 2-(,5-dihydroimidazolyl)-benzene, -quinoline, and -quinoxaline derivatives and 2-morpholino-4-catechol have been characterized as agonists or partial agonists for human platelet aggregation; and for inhibition of adenylate cyclase by measurement of their effect on platelet [cyclic-3',5'-AMP]. Antagonist activity for these compounds versus adrenaline as agonist has also been assessed for these two responses. The compounds can be divided into 4 groups. Group I contains compounds that are agonists for both responses; group II, compounds that are agonists for inhibition of adenylate cyclase but antagonists for the aggregatory response; group III, compounds that are agonists for the aggregatory response but are antagonists for inhibition of adenylate cyclase by adrenaline; and group IV, compounds that are antagonists for both responses. In group I the EC50 values for induction of aggregation are not significantly different from the EC50 values for inhibition of adenylate cyclase except for 2-morpholino-4-catechol which is significantly more potent as an inhibitor of adenylate cyclase. In group IV a linear correlation is observed between the K1 values for the two responses for 8 compounds but 2 other compounds do not conform to this correlation. The data are not consistent with a model in which a single chi 2-adrenoceptor mediates both the aggregatory response and inhibition of adenylate cyclase and hence support a model in which unique chi 2-adrenoceptors mediate these two responses.

UI MeSH Term Description Entries
D010208 Papaverine An alkaloid found in opium but not closely related to the other opium alkaloids in its structure or pharmacological actions. It is a direct-acting smooth muscle relaxant used in the treatment of impotence and as a vasodilator, especially for cerebral vasodilation. The mechanism of its pharmacological actions is not clear, but it apparently can inhibit phosphodiesterases and it may have direct actions on calcium channels. Cerespan,Papaverine Hydrochloride,Pavabid,Pavatym,Hydrochloride, Papaverine
D010974 Platelet Aggregation The attachment of PLATELETS to one another. This clumping together can be induced by a number of agents (e.g., THROMBIN; COLLAGEN) and is part of the mechanism leading to the formation of a THROMBUS. Aggregation, Platelet
D011458 Prostaglandins E (11 alpha,13E,15S)-11,15-Dihydroxy-9-oxoprost-13-en-1-oic acid (PGE(1)); (5Z,11 alpha,13E,15S)-11,15-dihydroxy-9-oxoprosta-5,13-dien-1-oic acid (PGE(2)); and (5Z,11 alpha,13E,15S,17Z)-11,15-dihydroxy-9-oxoprosta-5,13,17-trien-1-oic acid (PGE(3)). Three of the six naturally occurring prostaglandins. They are considered primary in that no one is derived from another in living organisms. Originally isolated from sheep seminal fluid and vesicles, they are found in many organs and tissues and play a major role in mediating various physiological activities. PGE
D001792 Blood Platelets Non-nucleated disk-shaped cells formed in the megakaryocyte and found in the blood of all mammals. They are mainly involved in blood coagulation. Platelets,Thrombocytes,Blood Platelet,Platelet,Platelet, Blood,Platelets, Blood,Thrombocyte
D004347 Drug Interactions The action of a drug that may affect the activity, metabolism, or toxicity of another drug. Drug Interaction,Interaction, Drug,Interactions, Drug
D004837 Epinephrine The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS. Adrenaline,4-(1-Hydroxy-2-(methylamino)ethyl)-1,2-benzenediol,Adrenaline Acid Tartrate,Adrenaline Bitartrate,Adrenaline Hydrochloride,Epifrin,Epinephrine Acetate,Epinephrine Bitartrate,Epinephrine Hydrochloride,Epinephrine Hydrogen Tartrate,Epitrate,Lyophrin,Medihaler-Epi,Acetate, Epinephrine
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000242 Cyclic AMP An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH. Adenosine Cyclic 3',5'-Monophosphate,Adenosine Cyclic 3,5 Monophosphate,Adenosine Cyclic Monophosphate,Adenosine Cyclic-3',5'-Monophosphate,Cyclic AMP, (R)-Isomer,Cyclic AMP, Disodium Salt,Cyclic AMP, Monoammonium Salt,Cyclic AMP, Monopotassium Salt,Cyclic AMP, Monosodium Salt,Cyclic AMP, Sodium Salt,3',5'-Monophosphate, Adenosine Cyclic,AMP, Cyclic,Adenosine Cyclic 3',5' Monophosphate,Cyclic 3',5'-Monophosphate, Adenosine,Cyclic Monophosphate, Adenosine,Cyclic-3',5'-Monophosphate, Adenosine,Monophosphate, Adenosine Cyclic
D000244 Adenosine Diphosphate Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position. ADP,Adenosine Pyrophosphate,Magnesium ADP,MgADP,Adenosine 5'-Pyrophosphate,5'-Pyrophosphate, Adenosine,ADP, Magnesium,Adenosine 5' Pyrophosphate,Diphosphate, Adenosine,Pyrophosphate, Adenosine
D000262 Adenylyl Cyclases Enzymes of the lyase class that catalyze the formation of CYCLIC AMP and pyrophosphate from ATP. Adenyl Cyclase,Adenylate Cyclase,3',5'-cyclic AMP Synthetase,Adenylyl Cyclase,3',5' cyclic AMP Synthetase,AMP Synthetase, 3',5'-cyclic,Cyclase, Adenyl,Cyclase, Adenylate,Cyclase, Adenylyl,Cyclases, Adenylyl,Synthetase, 3',5'-cyclic AMP

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