Protective Effect of Nitrous Oxide against Total-Body Radiation in the Mouse

IT has been shown that nitrous oxide and certain inert gases reduce oxygen-dependent radiosensitivity in broad bean roots and mouse Ehrlich ascites tumour cells in vitro 1 . Irradiation in one atmosphere of 80 per cent nitrous oxide with 20 per cent oxygen markedly reduced the radiosensitivity of mouse ascites tumour cells, as judged by chromosomal damage at anaphase. In a later investigation 2 , using a different criterion of tumour growth after a standard inoculum of cells irradiated in vitro into normal animals, protection was not afforded by this nitrous oxide–oxygen mixture at 1 atmosphere pressure. Data have not yet been presented on a protective effect at elevated pressure. They demonstrated that xenon, the most effective of the inert gases in reducing oxygen-dependent radiosensitivity, was protective only at pressures in excess of 1 atmosphere in these in vitro systems.