title: Exogenous GTP increases cyclic GMP and inhibits thrombin-induced aggregation of washed human platelets: comparison with ATP, adenosine and guanosine.
abstract: The effects of exogenous guanosine 5'-triphosphate (GTP), guanosine, adenosine 5'-triphosphate (ATP) and adenosine on platelet aggregation, serotonin secretion and cyclic nucleotide accumulation were studied using thrombin-stimulated washed human platelets. GTP (10 microM-1 mM) dose-dependently inhibited thrombin-induced aggregation and serotonin secretion. The inhibition of aggregation was accompanied by an increase in platelet cyclic GMP. GTP did not affect cyclic AMP concentration. Adenosine (1 microM-1 mM) dose-dependently inhibited thrombin-induced aggregation and serotonin secretion, and increased cyclic AMP. ATP at high concentrations (100 microM-1 mM) inhibited aggregation and serotonin secretion, and 1 mM ATP increased cyclic AMP. Guanosine was relatively ineffective in preventing aggregation and serotonin secretion and did not affect cyclic GMP. The rank order of inhibition of thrombin-induced aggregation of washed human platelets was adenosine > GTP > ATP > guanosine. In conclusion, exogenous GTP inhibits thrombin-induced aggregation and serotonin secretion of washed human platelets by increasing cyclic GMP. The results raise the possibility of a cell membrane site of action for GTP in platelets which mediates the activation of soluble guanylate cyclase suggesting that GTP may have a local antithrombotic effect also in vivo.
authors.affiliation: Department of Biomedical Sciences, University of Tampere, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Vuorinen
authors.forename: K E
authors.initials: KE
authors.lastname: Laustiola
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects*; D006152:Cyclic GMP / Q000378:metabolism*; D006151:Guanosine / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D012701:Serotonin / Q000378:metabolism; D013917:Thrombin / Q000037:antagonists & inhibitors* / Q000494:pharmacology
chemical_list: D010975:Platelet Aggregation Inhibitors; D006151:Guanosine; D012701:Serotonin; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D013917:Thrombin; D006152:Cyclic GMP; D000241:Adenosine