title: Gamma radiation effect on vascular smooth muscle cells in culture.
abstract: OBJECTIVE
  Prior work in our laboratory demonstrated that external gamma irradiation administered within 48 h following balloon catheter carotid artery injury in rats produced a marked inhibition of intimal hyperplasia and restenosis. The current study used smooth muscle cells (SMC) in vitro to examine the radiation dose response and to investigate the cellular mechanism by which radiation inhibits SMC proliferation.
  
  
  METHODS
  Quiescent rat aortic SMC in plasma were refed with whole blood serum to stimulate synchronous proliferation and immediately irradiated with single fraction doses of 1.25-20 Gy.
  
  
  RESULTS
  Comparison between a micronucleus assay and a clonogenic assay indicated a dose-dependent inhibition of SMC growth, with an ED50 at 2-3 Gy. The micronucleus assay also demonstrated a dose-dependent increase in apparent chromosomal damage at 72 h after irradiation. Inhibition of SMC growth by radiation did not correlate with changes in intracellular or released mitogenic activity. Furthermore, there was no evidence of apoptosis in irradiated SMC up to 96 h after treatment.
  
  
  CONCLUSIONS
  Radiation likely inhibits SMC proliferation after arterial injury by a dose-dependent mechanism of lethal and/or sublethal cellular injury leading to clonogenic cell death.
authors.affiliation: Department of Neurological Surgery, University of Washington, Seattle 98108, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Gajdusek
authors.forename: H
authors.initials: H
authors.lastname: Tian
authors.forename: S
authors.initials: S
authors.lastname: London
authors.forename: D
authors.initials: D
authors.lastname: Zhou
authors.forename: J
authors.initials: J
authors.lastname: Rasey
authors.forename: M R
authors.initials: MR
authors.lastname: Mayberg
mesh_terms: D000818:Animals; D017209:Apoptosis; D002455:Cell Division / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D003470:Culture Media; D004247:DNA / Q000032:analysis; D004307:Dose-Response Relationship, Radiation; D015162:Micronucleus Tests; D008934:Mitogens / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D051381:Rats
chemical_list: D003470:Culture Media; D008934:Mitogens; D004247:DNA