title: Reduced basal nitric oxide bioavailability and platelet activation in young spontaneously hypertensive rats.
abstract: OBJECTIVE
  To investigate the role of basal nitric oxide (NO) bioavailability for platelet activation in young spontaneously hypertensive rats before onset of hypertension. Phosphorylation of the vasodilator-stimulated phosphoprotein (VASP) in platelets was used as a sensitive monitor of in vivo NO bioavailability.
  
  
  RESULTS
  Whole blood samples were taken from 10-week-old Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). In vivo surface-expression of P-selectin and platelet-binding of fibrinogen were assessed by flow cytometry. Platelet VASP-phosphorylation at its serine 239 (Ser239) and serine 157 (Ser157) residues was assessed using specific antibodies to determine NO bioavailability in vivo, and compared with endothelial vasomotor function. The increment in vascular tone following inhibition of NO-synthase in slightly preconstricted aortic rings was reduced indicating less NO formation under physiological stimulation (WKY 71.1+/-4.1%; SHR 57.8+/-2.4%, P<0.05). In vivo platelet VASP-phosphorylation was significantly reduced at both phosphorylation sites in SHR (mean fluorescence for Ser239: WKY: 15.2+/-0.6; SHR: 11.7+/-0.5, P<0.01; Ser157: WKY: 53.0+/-3.0; SHR: 35.0+/-3.5, P<0.05). Surface-expression of P-selectin and membrane-bound fibrinogen were significantly enhanced in SHR compared with WKY (P-selectin: WKY: 23.2+/-3.4; SHR 58.3+/-7.9, P<0.001; platelet-bound fibrinogen: WKY: 8.6+/-0.5; SHR: 13.5+/-1.1, P<0.001). In vitro preincubation of platelets with the NO donor sodium nitroprusside normalized platelet surface-expression of P-selectin in SHR.
  
  
  CONCLUSIONS
  Using VASP-phosphorylation as a sensitive monitor of in vivo NO bioavailability, these data provide evidence that reduced vascular NO formation in vivo contributes to increased platelet activation in young SHR.
authors.affiliation: Medizinische Klinik der Julius-Maximilians-Universität, Würzburg, Germany. a.schaefer@medizin.uni-wuerzburg.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Schäfer
authors.forename: Julian
authors.initials: J
authors.lastname: Widder
authors.forename: Martin
authors.initials: M
authors.lastname: Eigenthaler
authors.forename: Georg
authors.initials: G
authors.lastname: Ertl
authors.forename: Johann
authors.initials: J
authors.lastname: Bauersachs
mesh_terms: D000818:Animals; D001682:Biological Availability; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D006973:Hypertension / Q000378:metabolism* / Q000473:pathology; D008840:Microfilament Proteins; D009569:Nitric Oxide / Q000493:pharmacokinetics* / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D015539:Platelet Activation; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D009569:Nitric Oxide