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Mepacrine-induced inhibition of human platelet cyclic-GMP phosphodiesterase. 1984

T Yamakado, and F Tanaka, and H Hidaka

The effect of mepacrine (DL-quinacrine-HCI), a specific inhibitor of phospholipase C, on cyclic-GMP levels in human platelets was investigated. The concentrations of mepacrine producing 50% inhibition of human platelet aggregation induced by 5 microM ADP and 3 micrograms/ml of collagen were 50 +/- 8 and 70 +/- 15 microM, respectively. Addition of mepacrine to human platelet suspension resulted in increases in cyclic GMP. In contrast to cyclic-GMP levels, cyclic-AMP content was not affected by mepacrine. Mepacrine did not stimulate guanylate cyclase, but did specifically inhibit human platelet cyclic-GMP phosphodiesterase, separated from cyclic-AMP phosphodiesterase or other forms of phosphodiesterase on DEAE-cellulose columns. Stimulation by cyclic GMP of human platelet cyclic-GMP-stimulated cyclic-AMP phosphodiesterase activity was not inhibited by mepacrine. The IC50 value of the drug for cyclic-GMP phosphodiesterase was 40 microM, and IC50 for cyclic-AMP phosphodiesterase was 1.2 mM. Mepacrine was 30-times more potent as an inhibitor of human platelet cyclic GMP than of cyclic-AMP phosphodiesterase. Mepacrine blocks arachidonate release from human platelets by inhibiting phosphatidylinositol-specific phospholipase C. The increase in cyclic-GMP levels produced by addition of mepacrine will explain part of the pharmacological action of this drug.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
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
D011796 Quinacrine An acridine derivative formerly widely used as an antimalarial but superseded by chloroquine in recent years. It has also been used as an anthelmintic and in the treatment of giardiasis and malignant effusions. It is used in cell biological experiments as an inhibitor of phospholipase A2. Mepacrine,Acrichine,Atabrine,Atebrin,Quinacrine Dihydrochloride,Quinacrine Dihydrochloride, Dihydrate,Quinacrine Dihyrochloride, (R)-Isomer,Quinacrine Dihyrochloride, (S)-Isomer,Quinacrine Dimesylate,Quinacrine Hydrochloride,Quinacrine Monoacetate,Quinacrine Monohydrochloride,Quinacrine Monomesylate,Quinacrine, (+-)-Isomer,Quinacrine, (R)-Isomer,Quinacrine, (S)-Isomer,Dihydrochloride, Quinacrine,Dimesylate, Quinacrine,Hydrochloride, Quinacrine,Monoacetate, Quinacrine,Monohydrochloride, Quinacrine,Monomesylate, Quinacrine
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
D006162 Guanylate Cyclase An enzyme that catalyzes the conversion of GTP to 3',5'-cyclic GMP and pyrophosphate. It also acts on ITP and dGTP. (From Enzyme Nomenclature, 1992) EC 4.6.1.2. Guanyl Cyclase,Deoxyguanylate Cyclase,Guanylyl Cyclase,Inosinate Cyclase,Cyclase, Deoxyguanylate,Cyclase, Guanyl,Cyclase, Guanylate,Cyclase, Guanylyl,Cyclase, Inosinate
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
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
D015106 3',5'-Cyclic-GMP Phosphodiesterases Enzymes that catalyze the hydrolysis of cyclic GMP to yield guanosine-5'-phosphate. 3',5'-Cyclic GMP 5'-Nucleotidohydrolase,3',5'-Cyclic GMP Phosphodiesterase,3',5'-Cyclic-GMP Phosphodiesterase,3,5-Cyclic GMP 5-Nucleotidohydrolase,3,5-Cyclic GMP Phosphodiesterase,3',5' Cyclic GMP 5' Nucleotidohydrolase,3',5' Cyclic GMP Phosphodiesterase,3',5' Cyclic GMP Phosphodiesterases,3,5 Cyclic GMP 5 Nucleotidohydrolase,3,5 Cyclic GMP Phosphodiesterase,5'-Nucleotidohydrolase, 3',5'-Cyclic GMP,5-Nucleotidohydrolase, 3,5-Cyclic GMP,GMP 5'-Nucleotidohydrolase, 3',5'-Cyclic,GMP 5-Nucleotidohydrolase, 3,5-Cyclic,GMP Phosphodiesterase, 3',5'-Cyclic,GMP Phosphodiesterase, 3,5-Cyclic,Phosphodiesterase, 3',5'-Cyclic GMP,Phosphodiesterase, 3',5'-Cyclic-GMP,Phosphodiesterase, 3,5-Cyclic GMP,Phosphodiesterases, 3',5'-Cyclic-GMP

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