Damage to the reproductive capacity of human cells in tissue culture by ionizing radiations of different linear energy transfer

Barendsen, G.W.

R J C Harris, Editor The Initial Effects of Ionizing Radiations on Cells 183-194


Accession: 024437763

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Kidney cells of human origin, cultured by the Puck technique were irradiated with ɑ, β, 200 kV X- and 20 kV X-radiation, in special dishes with a Melinex bottom 6μ thick, which per-mitted irradiation from outside with alpha particles from Po210 and beta particles from Y90. The number of cells, which after irradiation had retained the capacity for clone formation, was counted. The survival curve was exponential in the case of ɑ-irradiation, whereas with other radiations a more complicated curve was obtained, which cannot be interpreted by a 2-hit mechanism. The RBE of ɑ-radiation ranged from 2.5 at high doses to 6.0 at low doses. With ɑ-radiation the sensitive area of these cells for the inhibition of clone formation was calculated to be 40μ2, which is approximately equal to the cross-sectional area of the nuclei. It may be inferred that clone formation is inhibited if one ɑ-particle passes somewhere through the nucleus. Fractionated doses showed that partial repair takes place after X-and β-irradiation, but no recovery could be detected after ɑ-irradiation. Cells were also irradiated with ɑ -radiation followed by X-irradiation and conversely. No departure from additivity was observed, i.e., X-radiation acts on cells surviving after ɑ-irradiation as if they were not irradiated at all. This contrasts with the effect of a second dose of X-radiation, which depends on the amount of X-radiation the cells have received before, i.e., in this case there is some cumulative effect. The sensitivity of these cells to ɑ- and X-radiation when in equilibrium with different mixtures of N and O is discussed. Absence of oxygen protects the cells in X-irradiation experiments but a very small decrease in sensitivity is found with ɑ-radiation.