title: Reduction in clonogenic survival of sodium-iodide symporter (NIS)-positive cells following intracellular uptake of (99m)Tc versus (188)Re.
abstract: OBJECTIVE
  Cellular radionuclide uptake increases the heterogeneity of absorbed dose to biological structures. Dose increase depends on uptake yield and emission characteristics of radioisotopes. We used an in vitro model to compare the impact of cellular uptake of (188)Re-perrhenate and (99m)Tc-pertechnetate on cellular survival.
  
  
  METHODS
  Rat thyroid PC Cl3 cells in culture were incubated with (188)Re or (99m)Tc in the presence or absence of perchlorate for 1 hour. Clonogenic cell survival was measured by colony formation. In addition, intracellular radionuclide uptake was quantified.
  
  
  RESULTS
  Dose effect curves were established for (188)Re and (99m)Tc for various extra- and intracellular distributions of the radioactivity. In the presence of perchlorate, no uptake of radionuclides was detected and (188)Re reduced cell survival more efficiently than (99m)Tc. A(37), the activity that is necessary to yield 37% cell survival was 14 MBq/ml for (188)Re and 480 MBq/ml for (99m)Tc. In the absence of perchlorate, both radionuclides showed similar uptakes; however, A(37) was reduced by 30% for the beta-emitter and by 95% for (99m)Tc. The dose D(37) that yields 37% cell survival was between 2.3 and 2.8 Gy for both radionuclides.
  
  
  CONCLUSIONS
  Uptake of (188)Re and (99m)Tc decreased cell survival. Intracellular (99m)Tc yielded a dose increase that was higher compared to (188)Re due to emitted Auger and internal conversion-electrons. Up to 5 Gy there was no difference in radiotoxicity of (188)Re and (99m)Tc. At doses higher than 5 Gy intracellular (99m)Tc became less radiotoxic than (188)Re, probably due to a non-uniform lognormal radionuclide uptake.
authors.affiliation: University Hospital/Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Department of Nuclear Medicine, Dresden, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Freudenberg
authors.forename: Maria
authors.initials: M
authors.lastname: Wendisch
authors.forename: Roswitha
authors.initials: R
authors.lastname: Runge
authors.forename: Gerd
authors.initials: G
authors.lastname: Wunderlich
authors.forename: Jörg
authors.initials: J
authors.lastname: Kotzerke
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000528:radiation effects; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D005110:Extracellular Space / Q000378:metabolism / Q000528:radiation effects; D042541:Intracellular Space / Q000378:metabolism* / Q000528:radiation effects*; D009010:Monte Carlo Method; D015609:Organotechnetium Compounds / Q000378:metabolism*; D011868:Radioisotopes / Q000378:metabolism*; D011874:Radiometry; D051381:Rats; D012211:Rhenium / Q000378:metabolism*; D027981:Symporters / Q000378:metabolism*; D013961:Thyroid Gland / Q000166:cytology; D000099209:Sodium-Iodide Symporters
chemical_list: D015609:Organotechnetium Compounds; D011868:Radioisotopes; D012211:Rhenium; D027981:Symporters; D000099209:Sodium-Iodide Symporters