The effect of nitrous oxide on the cell cycle in human bone marrow

The effect of 24 h exposure to nitrous oxide on the cell division cycle in human bone marrow has been studied in vivo using the technique of DNA flow microfluorimetry. All patients who received nitrous oxide showed a significant increase in the proportion of early S-phase cells with a decrease in late S, G2 and mitotic cells. These changes resemble those seen following the use of S-phase-specific cytotoxic drugs. Control patients showed no such effect. Parallel studies have suggested that interference with the function of vitamin B12 underlies this response. Nitrous oxide may provide a convenient method for studying the cell kinetic aspects of acute B12 deficiency and the possibility of using it to increase the therapeutic index of antitumour drugs is discussed.