Hematopoietic and nonhematopoietic cell lines cultured in media containing either 5-methyltetrahydrofolate or 5-formyltetrahydrofolate grow well to the same extent. However, when these same cell lines are grown in the presence of nitrous oxide, selective growth inhibition can be shown for hematopoietic cells cultured in 5-methyltetrahydrofolate-containing media. These cells also demonstrated a ...