title: Thrombin-induced mitogenesis in cultured aortic smooth muscle cells requires prolonged thrombin exposure.
abstract: Thrombin has been implicated in vascular smooth muscle cell (VSMC) proliferation after vessel injury. Its proliferative effects, which are mediated via proteolytic activation of a receptor similar or identical to the cloned thrombin receptor (TR), have markedly delayed kinetics. The present study demonstrates that, despite rapid thrombin receptor activation and similar time to S phase entry compared with classic polypeptide growth factors, prolonged thrombin exposure is required to promote maximal VSMC mitogenesis. Flow cytometric analysis of thrombin-stimulated cells revealed that thrombin induced a progressive increase in the growth fraction over 3 days in culture, an effect that was blocked by hirudin even late after thrombin addition. Northern blot hybridization after thrombin stimulation demonstrated that thrombin upregulates TR mRNA expression within 6 h. These findings indicate that VSMC proliferate in response to prolonged thrombin exposure and suggest that the mitogenic delay may involve not only the thrombin-dependent synthesis and activation of newly made TR but also the progressive thrombin-dependent recruitment of cells into the growth fraction.
authors.affiliation: Department of Medicine, University of Virginia, Charlottesville 22908, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Bachhuber
authors.forename: I J
authors.initials: IJ
authors.lastname: Sarembock
authors.forename: L W
authors.initials: LW
authors.lastname: Gimple
authors.forename: C A
authors.initials: CA
authors.lastname: McNamara
authors.forename: G K
authors.initials: GK
authors.lastname: Owens
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects*; D001483:Base Sequence; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D008934:Mitogens / Q000494:pharmacology*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018179:Receptors, Thrombin / Q000235:genetics; D016196:S Phase; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D008934:Mitogens; D015335:Molecular Probes; D012333:RNA, Messenger; D018179:Receptors, Thrombin; D013917:Thrombin