title: Relative biological effectiveness (RBE) of 210Po alpha-particles versus X-rays on lethality in bovine endothelial cells.
abstract: OBJECTIVE
  Alpha-radiation from polonium-210 ((210)Po) can elevate background radiation dose by an order of magnitude in people consuming large quantities of meat and seafood, particularly caribou and reindeer. Because up to 50% of the ingested (210)Po body burden is initially found in the blood, a primary target for the short range alpha-particles is the endothelial cells lining the blood vessels. This study examined the relative biological effectiveness (RBE) of (210)Po alpha-particles versus 250 kVp X-rays in producing injury to cultured bovine aortic endothelial cells.
  
  
  METHODS
  Radiation effects on cells were measured in four different ways: the percentage viable cells by trypan blue dye exclusion, the number of live cells, the lactate dehydrogenase (LDH) release to medium and the ability to form colonies (clonogenic survival).
  
  
  RESULTS
  Comparison of dose-response curves yielded RBE values of 13.1+/-2.5 (SEM) for cell viability, 10.3+/-1.0 for live cell number and 11.1+/-3.0 for LDH activity. The RBE values for clonogenic survival were 14.0+/-1.0 based on the ratio of the initial slopes of the dose-response curves and 13.1, 9.9 and 7.7 for 50, 10 and 1% survival rate, respectively. At X-ray doses <0.25 Gy, a pronounced stimulatory effect on proliferation was noted.
  
  
  CONCLUSIONS
  Exposure to (210)Po alpha-particles was seven to 14 times more effective than X-ray exposure in causing endothelial cell damage.
authors.affiliation: Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5B3.
authors.forename: P A
authors.initials: PA
authors.lastname: Thomas
authors.forename: B L
authors.initials: BL
authors.lastname: Tracy
authors.forename: T
authors.initials: T
authors.lastname: Ping
authors.forename: M
authors.initials: M
authors.lastname: Wickstrom
authors.forename: N
authors.initials: N
authors.lastname: Sidhu
authors.forename: L
authors.initials: L
authors.lastname: Hiebert
mesh_terms: D000512:Alpha Particles / Q000009:adverse effects; D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004730:Endothelium, Vascular / Q000166:cytology / Q000293:injuries / Q000528:radiation effects*; D020387:Food Chain; D005507:Food Contamination, Radioactive; D006801:Humans; D008854:Microscopy, Electron; D011059:Polonium / Q000009:adverse effects / Q000097:blood; D012062:Relative Biological Effectiveness; D014965:X-Rays / Q000009:adverse effects*
chemical_list: D011059:Polonium