title: Cellular mechanisms of cyclic nucleotide-induced vasorelaxation.
abstract: OBJECTIVE
  Endothelial-derived vasorelaxants such as prostacyclin and nitric oxide (NO) induce vascular smooth muscle relaxation through activation of cyclic nucleotide-dependent cellular signalling pathways. However, the specific events that lead to dissociation of actin and myosin and relaxation are not known. The purpose of this investigation was to determine the late phase signaling events that modulate vascular smooth muscle relaxation.
  
  
  METHODS
  Fresh bovine carotid artery smooth muscle (BCASM) contractile responses were determined in a muscle bath under Ca(2+)-containing and Ca(2+)-free conditions. Physiologic responses were correlated with phosphorylation events using whole cell phosphorylation and two-dimensional gel electrophoresis.
  
  
  RESULTS
  Cyclic nucleotide-dependent vasorelaxation can occur without detectable changes in intracellular Ca2+ concentrations. However, vascular smooth muscles that had been precontracted with the phosphatase inhibitor calyculin were refractory to relaxation. Vascular smooth muscle relaxation was associated with an increase in the phosphorylation of two 20 kDa proteins under Ca(2+)-containing and Ca(2+)-free conditions.
  
  
  CONCLUSIONS
  These results suggest that Ca(2+)-independent mechanisms may also modulate vascular smooth muscle relaxation. Two possible late phase signaling mechanisms include phosphatase activation and an increase in the phosphorylation of two 20 kDa phosphoproteins.
authors.affiliation: Department of Surgery, Medical College of Georgia, Augusta 30912, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Brophy
authors.forename: E G
authors.initials: EG
authors.lastname: Whitney
authors.forename: S
authors.initials: S
authors.lastname: Lamb
authors.forename: A
authors.initials: A
authors.lastname: Beall
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002339:Carotid Arteries; D002417:Cattle; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000502:physiology; D009126:Muscle Relaxation / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000502:physiology*; D009712:Nucleotides, Cyclic / Q000502:physiology*; D010766:Phosphorylation; D015398:Signal Transduction; D014661:Vasoconstriction / Q000502:physiology
chemical_list: D009712:Nucleotides, Cyclic; D017869:Cyclic GMP-Dependent Protein Kinases; D002118:Calcium