Figure 3.

Effects of l-Arg on oxygen radical formation and iNOS expression. (A) Relationship between intracellular l-Arg levels (open bars) and oxygen radical production (filled bars) in macrophages. Control, normal cultured cells; LPS + IFN-γ, cells after 24-hr activation in DMEM; l-Arg depletion, cells incubated in l-Arg-free medium for 24 hr; LPS + IFN-γ and l-Arg depletion, cells after 24-hr activation in l-Arg-free medium. Data are expressed as mean ± SEM obtained from three experiments. (B) Western blot analysis of iNOS protein in nonactivated cells and cells activated in the presence or absence of l-Arg. While no iNOS could be detected in nonactivated cells, identical amounts of iNOS protein were observed in cells activated by LPS and IFN-γ in either normal DMEM or l-Arg-free medium.