Effect of culture P-O2 on macrophage (RAW 264.7) nitric oxide production

Macrophages are commonly cultured at a Po-2 of 149 Torr, but tissue macroph ages in vivo live in an environment of much lower oxygen tension. Despite t he many potential mechanisms for changes in oxygen tension to influence nit ric oxide (NO) synthesis, there have been few reports investigating the eff ect of Po-2 on macrophage NO production. With the use of a culture chamber designed to rigorously control oxygen tension, we investigated the effects of culture Po-2 on macrophage NO production, inducible nitric oxide synthas e (iNOS) activity, iNOS protein, and tumor necrosis factor production. NO p roduction and iNOS activity were linearly related in the range of 39.4 to 6 77 Torr, but not in the range of 1.03 to 39.4 Torr. Therefore, results obta ined in vitro for the high oxygen tensions commonly used in cell culture we re quantitatively and qualitatively different from results obtained in cell s cultured at the lower oxygen tensions that more accurately reflect the in vivo environment. The influence of oxygen tension on NO production has imp lications for cell culture methodology and for the relationship between mic rocirculatory dysfunction and inflammatory responses in rodent models of se psis.