title: Cooperative effect of GNB3 825C>T and GPIIIa PI(A) polymorphisms in enhanced platelet aggregation.
abstract: BACKGROUND
  Platelet aggregation contributes to various thrombembolic disorders. Environmental factors affect platelet aggregability but only partially explain the interindividual variability in aggregation. While the platelet glycoprotein IIb/IIIa is involved in the pathogenesis of acute coronary syndromes whereas most platelet activating stimuli act via G Protein coupled receptors we investigated whether the 825C>T polymorphism of the gene GNB3 encoding the G protein beta3 subunit together with the platelet glycoprotein (GP) IIIa Pl(A) polymorphism are predictive of platelet aggregability on stimulation with various agonists acting via GPCRs.
  
  
  METHODS
  Platelet aggregation was measured by turbidometry in 150 non-smoking individuals aged 18-40 years at a density of 2 x 10(5) platelets/microl with various agonists according to the method of Born. Genotypes of the GNB3 825C>T and glycoprotein IIb/IIIa PI(A) polymorphisms were determined using Pyrosequencing technology and restriction analysis. All functional studies were completed within 3 h. The data were analysed by Student's t-test for paired data.
  
  
  RESULTS
  Low concentrations of agonists resulted in enhanced platelet aggregation in subjects with the GNB3 CC-genotype compared to carriers of a 825T-allele. This effect was further enhanced in carriers of the GPIIIa Pl(A2) allele (2 microM ADP: 42% vs. 19%, p=0.017; 1 microM U-46619: 51% vs. 30%, p=0.03; 5 microM epinephrine: 69% vs. 53%, p=0.025). No significant pattern of aggregation was observed on stratification by GPIIIa genotypes alone.
  
  
  CONCLUSIONS
  Our findings indicate that two genetic markers contribute synergistically to increased platelet aggregation. This will help to identify patients at increased risk for thrombosis.
authors.affiliation: Institut für Pharmakologie, Universitätsklinikum, D-45122, Essen, Germany. ulrich.frey@uni.essen.de
authors.forename: Ulrich H
authors.initials: UH
authors.lastname: Frey
authors.forename: Nese
authors.initials: N
authors.lastname: Aral
authors.forename: Norbert
authors.initials: N
authors.lastname: Müller
authors.forename: Winfried
authors.initials: W
authors.lastname: Siffert
mesh_terms: D000328:Adult; D000483:Alleles; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D039661:Integrin beta3 / Q000235:genetics / Q000502:physiology*; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects / Q000235:genetics*; D011110:Polymorphism, Genetic; D019851:Thrombophilia / Q000235:genetics*
chemical_list: C454420:G-protein beta3 subunit; D039661:Integrin beta3; D020962:Heterotrimeric GTP-Binding Proteins; D004837:Epinephrine