[Lethal effect of the decay of 64Cu and 67Cu incorporated in mammalian cells]

A high lethal efficiency was observed when the decay of two radioactive isotopes of copper, 64Cu or 67Cu, occurred in mammalian cells. The lethal efficiency is of the same order for both isotopes in spite of their different decay processes. As the lethal event could be attributed to an injury inside the cellular DNA only, these results suggest that, even if present in the DNA in trace amounts solely, copper atoms are essential chromatin components. Their behaviour differs depending on whether the cell is a tumor or a non tumor cell because their lethal efficiencies are different (0.5 and 0.1 respectively).