Intracellular distribution and radiotoxicity of chromium-51 in mammalian cells: Auger-electron dosimetry.

The kinetics of uptake and of radiotoxicity of chromium-51, an Auger-electron emitter, have been studied in V79 lung fibroblasts of the Chinese hamster. Intracellular radioactivity was directly proportional to the incubation period and to the extracellular concentration of the Cr-51. About 14% of the cellular activity was associated with the nucleus, whereas approximately 2% was guanidine-precipitable and therefore bound to DNA. The growth rate of V79 cells was slowed following intracellular incorporation of Cr-51. The cell-survival curve, in terms of colony-forming ability, was of the low-LET type, with a D37 of 6.2 pCi/cell. Theoretical dosimetric estimates indicate that, under the given experimental conditions, the mean lethal dose to the cell nucleus was 870 rad. Although this value is somewhat larger than the x-ray D37 dose of 580 rad for this cell line, it is more realistic than the gross underestimate obtained by classical MIRD calculations (2-3 rad/cell).