In-vivo radiotoxicity of DNA-incorporated 125I compared with that of densely ionising alpha-particles.

When the atomic nucleus of 125I decays by orbital electron capture followed by internal conversion, numerous very-low-energy electrons (Auger electrons) are emitted, so that the energy density in the immediate vicinity of the decay site is extremely high. 125I incorporated into DNA was as effective as densely ionising 5.3 MeV alpha-particles from 210Po in reducing the sperm-head population in mice.

Radioimmunotherapy of human colonic cancer xenografts with 90Y labeled monoclonal antibodies to carcinoembryonic antigen.

Monoclonal antibodies (MAbs) to carcinoembryonic antigen (CEA) or alpha-fetoprotein (AFP) were conjugated with diethylenetriaminepentaacetic acid and radiolabeled with 90Y at a specific activity of 4.0-6.0 mCi/mg.

Cytotoxicity of some indium radiopharmaceuticals in mouse testes.

The biological effects of [111In]oxine, [111In]citrate, and [114mIn]citrate localized in mouse testes as well as the effects of external x-rays are investigated. The in vivo radiotoxicity of [111In] oxine is far greater than the chemotoxicity of oxine. Of these radiolabeled compounds, [111In] oxine is the most effective in reducing the sperm-head population, the mean lethal dose (D37) to the organ being about 0.

In vivo effects of iron-55 and iron-59 on mouse testes: biophysical dosimetry of Auger electrons.

When the Auger-electron emitter, 55Fe, and the beta-emitter, 59Fe, are similarly distributed in the testes of mice, the conventionally calculated average radiation dose to the organ from 55Fe is about 2.6 times more effective in reducing the sperm-head count than the dose from 59Fe. This finding emphasizes the ability of low-energy Auger electrons to damage radiosensitive targets of cells through localized irradiation.

Radiotoxicity of thallium-201 in mouse testes: inadequacy of conventional dosimetry.

When TI-201 is concentrated in mouse testes, the low-energy Auger electrons following its electron-capture decay are found to be much more effective in causing loss of testicular weight and reduction of sperm heads than the energetic beta particles from similarly distributed TI-204. These results are contrary to expectations based on conventional dosimetry of tissue-incorporated radionuclides, and point to possible underestimation of risks by the currently adopted dosimetric procedures, especially in the case of radionuclides decaying by electron capture and internal conversion.