[Inhibition of hemopoiesis by nitrous oxide]

Inhibition of hemopoiesis by nitrous oxide was studied in mice and the following results were obtained. 1) During exposure to N2O, the numbers of pluripotent hemopoietic stem cells (CFU-S) and granulocyte-macrophage progenitor cells (GM-CFC) decreased significantly in the murine spleen and bone marrow, but the former more than the latter. 2) The recovery of CFU-S and GM-CFC was delayed in mice that were given low-dose irradiation followed by continuous exposure to N2O. The delay of recovery was significantly more in the spleen than in the bone marrow. 3) The levels of serum granulocyte-macrophage colony stimulating factor (CSF) in N2O exposed mice, induced by endotoxin, decreased significantly compared with those of control mice. Prolonged N2O administration to mice appears to impair the hemopoietic inductive microenvironment as well as hemopoietic stem cells and hence results in hemopoietic death and delay of hemopoietic recovery after irradiation.