Effect of nitrous oxide on human bone marrow cells and its synergistic effect with methionine and methotrexate on functional folate deficiency.

5-Methyltetrahydrofolate homocysteine methyltransferase activity in human bone marrow cells obtained from patients undergoing surgical operation became low after about 4 hr of nitrous oxide (N2O) anesthesia. The deoxyuridine suppression test performed on these bone marrow cells also became abnormal after about 6 hr of N2O anesthesia. The incorporation of [3H]thymidine into DNA in the bone marrow cells preincubated with methionine or methotrexate was much higher after N2O anesthesia than before anesthesia. Since N2O and methionine or methotrexate have a synergistic effect on depletion of functional folate, N2O alone or in combination with methionine or methotrexate might be of value for cancer treatment and deserve clinical trials.