title: Potent platelet antiaggregant action of an antiarrhythmic peptide (AAP).
abstract: A potent platelet antiaggregant action of an antiarrhythmic peptide (AAP) was demonstrated to be a cause of the antithrombotic effect. AAP (10, 20 or 40 mg/kg, i.v.) inhibited ex vivo platelet aggregation induced by collagen in a dose-dependent manner. AAP also inhibited the platelet aggregation of platelet-rich plasma (PRP) induced by collagen, Ca-ionophore A-23187, adenosine diphosphate (ADP), thrombin or arachidonic acid in vitro. The IC50 was 2.5 mM for collagen, 1.7 mM for A-23187, 5 mM for ADP, 0.4 mM for thrombin and 0.15 mM for arachidonic acid. The aggregation inhibitory activity of the peptide on washed platelet (WP), in a Ca2+-free medium, was stronger than on PRP. The IC50 was 1 mM for collagen and 20 microM for A-23187. No significant difference was found between antiaggregant activities of platelet-free plasma (PFP) from AAP-treated rats and PFP from normal rats supplemented with AAP. The direct action of AAP on platelets was also supported by the incorporation of AAP into platelet cytoplasma which caused a decrease of Ca2+-dependent 3':5'-cyclic nucleotide phosphodiesterase (Ca-PDE) activity. It was considered that AAP showed its platelet aggregation inhibitory activity by decreasing intracellular Ca2+ concentration through the inhibition of Ca-PDE activity.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D003094:Collagen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008297:Male; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D009842:Oligopeptides; C029579:antiarrhythmic peptide; D003094:Collagen; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D002118:Calcium