Biological effect of lead-212 localized in the nucleus of mammalian cells: Role of recoil energy in the radiotoxicity of internal alpha-particle emitters
- Univ. of Medicine & Dentistry of New Jersey, Newark, NJ (United States)
- Univ. of Massachusetts, Amherst, MA (United States)
The radiochemical dipyrrolidinedithiocarbamato-{sup 212}Pb(II) [{sup 212}Pb(PDC){sub 2}] is synthesized and its effects on colony formation in cultured Chinese hamster V79 cells are investigated. The cellular uptake, biological retention, subcellular distribution and cytotoxicity of the radiocompound are determined. The {sup 212}Pb is taken up quickly by the cells, reaching saturation levels in 1.25 h. When the cells are washed, the intracellular activity is retained with a biological half-life of 11.6 h. Gamma-ray spectroscopy indicates that the {sup 212}Pb daughters ({sup 212}Bi, {sup 212}Po and {sup 208}Tl) are in secular equilibrium within the cell. About 72% of the cellular activity localizes in the cell nucleus, of which 35% is bound specifically to nuclear DNA. The mean cellular uptake required to achieve 37% survival is 0.35 mBq of {sup 212}Pb per cell, which delivers a dose of 1.0 Gy to the cell nucleus when the recoil energy of {sup 212}Bi and {sup 212}Po decays is ignored and 1.7 Gy when recoil is included. The corresponding RBE values compared to acute external {sup 137}Cs {gamma} rays at 37% survival are 4.0 and 2.3, respectively. The chemical Pb(PDC){sub 2} is not chemotoxic at the concentrations used in this study. Because the {beta}-particle emitter {sup 212}Pb decays to the {alpha}-particle-emitting daughters {sup 212}Bi and {sup 212}Po, these studies provide information on the biological effects of {alpha}-particle decays that occur in the cell nucleus. Our earlier studies with cells of the same cell line using {sup 210}Po (emits 5.3 MeV {alpha} particle) localized predominantly in the cytoplasm resulted in an RBE of 6. These earlier results for {sup 210}Po, along with the present results for {sup 212}Pb, suggest that the recoil energy associated with the {sup 21}Bi and {sup 212}Po daughter nuclei plays little or no role in imparting biological damage to critical targets in the cell nucleus. 26 refs., 7 figs., 2 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 70212
- Journal Information:
- Radiation Research, Vol. 140, Issue 2; Other Information: PBD: Nov 1994
- Country of Publication:
- United States
- Language:
- English
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