title: Xanthines inhibit human platelet aggregation induced by platelet-activating factor.
abstract: 1. Platelet-activating factor (PAF) may be involved in the pathogenesis of asthma, and therefore the effects of the anti-asthma drugs theophylline and enprofylline on human platelet aggregation and adenosine triphosphate (ATP) release induced by PAF and adenosine diphosphate (ADP) were studied. 2. Enprofylline (50% inhibitory concentration [IC50] = 94.8 +/- 13.2 mumol/L) was more potent than theophylline (IC50 = 934.1 +/- 40.1 mumol/L) as an inhibitor of PAF-induced aggregation, and the xanthines were twice as potent as inhibitors of PAF-induced aggregation when compared with ADP-induced aggregation. ATP release was 1.4 times more sensitive to inhibition by the xanthines than aggregation. 3. Although high concentrations of xanthines inhibited platelet aggregation and ATP release induced by PAF, therapeutic concentrations are unlikely to inhibit PAF-induced effects.
authors.affiliation: Department of Medicine, University of Western Australia, Queen Elizabeth II Medical Centre, Nedlands.
authors.forename: N L
authors.initials: NL
authors.lastname: Misso
authors.forename: P J
authors.initials: PJ
authors.lastname: Thompson
mesh_terms: D000244:Adenosine Diphosphate / Q000097:blood / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000097:blood / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D013806:Theophylline / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology*
chemical_list: D010972:Platelet Activating Factor; D010975:Platelet Aggregation Inhibitors; D014970:Xanthines; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D013806:Theophylline; C034347:enprofylline