title: The effects of siguazodan, a selective phosphodiesterase inhibitor, on human platelet function.
abstract: 1. The effects of siguazodan (SK&F 94836) a selective phosphodiesterase (PDE) inhibitor with inotropic and vasodilator activity, were studied on human platelets. 2. Siguazodan selectively inhibited the major cyclic AMP-hydrolysing PDE in human platelet supernatants. The inhibited enzyme has been variously termed cyclic GMP-inhibited PDE or PDE-III. 3. In platelet-rich plasma (PRP), siguazodan inhibited U46619-induced aggregation more potently than that induced by ADP and collagen. Treatment of the PRP with aspirin had no effect on the potency of siguazodan. 4. In washed platelets, siguazodan increased cyclic AMP levels and reduced cytoplasmic free calcium [( Ca2+]i). ADP decreased the ability of siguazodan to raise cyclic AMP and this may explain its lower potency in inhibiting responses to ADP. 5. Siguazodan has anti-platelet actions over the same concentration range that it is an inotrope and vasodilator.
authors.affiliation: Department of Cellular Pharmacology, Smith Kline & French Research Ltd., The Frythe, Welwyn, Herts.
authors.forename: K J
authors.initials: KJ
authors.lastname: Murray
authors.forename: P J
authors.initials: PJ
authors.lastname: England
authors.forename: T J
authors.initials: TJ
authors.lastname: Hallam
authors.forename: J
authors.initials: J
authors.lastname: Maguire
authors.forename: K
authors.initials: K
authors.lastname: Moores
authors.forename: M L
authors.initials: ML
authors.lastname: Reeves
authors.forename: A W
authors.initials: AW
authors.lastname: Simpson
authors.forename: T J
authors.initials: TJ
authors.lastname: Rink
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000244:Adenosine Diphosphate / Q000378:metabolism; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D003094:Collagen / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010979:Platelet Function Tests; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D011724:Pyridazines / Q000494:pharmacology*
chemical_list: D006146:Guanidines; D010726:Phosphodiesterase Inhibitors; D010975:Platelet Aggregation Inhibitors; D011450:Prostaglandin Endoperoxides, Synthetic; D011724:Pyridazines; C056215:siguazodan; D000244:Adenosine Diphosphate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D003094:Collagen; D000242:Cyclic AMP; D001241:Aspirin; D002118:Calcium