Immunochemical detection of inducible NO synthase in human lung.

Type II (inducible) nitric oxide synthase (NOS) may play an important role in pulmonary pathophysiology, yet it remains controversial whether human tissues are capable of expressing this protein. Therefore, a polyclonal antibody (8196) was raised against type II NOS from induced RAW 264.7 macrophages and used to investigate the expression of this enzyme in human lung tissue. Anti-type II NOS antibody did not cross-react with either neuronal (type I) or endothelial (type III) constitutive NOS, whereas a 130-kDa protein was detected in cytosol from induced macrophages or liver removed from lipopolysaccharide (25 mg/kg)-treated rats. Cells or tissues that lacked NOS activity did not express immunoreactive proteins. Similarly, in grossly normal human lung tissue, no immunoreactivity was detected with the anti-type II NOS antibody. In contrast, strong immunoreactivity was detected in alveolar macrophages present in lung tissue from a patient with bronchiectasis and acute bronchopneumonia. These data demonstrate that human alveolar macrophages are able to express type II NOS and support a role for this enzyme in pulmonary inflammatory pathophysiology.