Characterization of the isoenzymes of cyclic nucleotide phosphodiesterase in human platelets and the effects of E4021.
In extracts of human platelets, three isoenzymes of cyclic nucleotide phosphodiesterase (PDE), namely, PDE2, PDE3, and PDE5, were identified; activities of PDE1 and PDE4 were not detected. In human platelets, the cGMP-hydrolytic activity was about six times higher than the cAMP-hydrolytic activity, and PDE5 and PDE3 are the major phosphodiesterase isoenzymes that hydrolyze cGMP and cAMP, respectively. PDE5 exhibited organ-specific expression in humans, and platelets were among the tissues richest in PDE5. A novel inhibitor of PDE5, sodium 1-[6-chloro-4-(3,4-methylenedioxybenzyl)aminoquinazolin-2-yl ] piperidine-4-carboxylate sesquihydrate (E4021), was a potent and highly selective inhibitor of human platelet PDE5. However, E4021 (up to 10 microM) did not inhibit 9,11-epithio-11,12-methano-thromboxane A2-induced platelet aggregation, in vitro. E4021 plus SIN-1 (3-morpholino-sydnonimine), at concentrations that had little effect individually, inhibited aggregation. These results suggest the unique distribution of phosphodiesterase isoenzymes in human platelets and the PDE5 inhibitors might be useful as a new class of antiplatelet drugs.
Ito
M
M
First Department of Internal Medicine, Mie University School of Medicine, Japan.
Nishikawa
M
M
Fujioka
M
M
Miyahara
M
M
Isaka
N
N
Shiku
H
H
Nakano
T
T
D015106:3',5'-Cyclic-GMP Phosphodiesterases; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000097:blood* / Q000302:isolation & purification; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000097:blood* / Q000302:isolation & purification; D010793:Phthalazines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D015398:Signal Transduction; D013928:Thromboxane A2 / Q000031:analogs & derivatives / Q000494:pharmacology; D014018:Tissue Distribution
C091517:E 4021; D007527:Isoenzymes; D010726:Phosphodiesterase Inhibitors; D010793:Phthalazines; D010880:Piperidines; D010975:Platelet Aggregation Inhibitors; D011799:Quinazolines; D013928:Thromboxane A2; C002385:linsidomine; C037866:STA 2; D008981:Molsidomine; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human; C052490:MY 5445