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 whethe r human tissues are capable of expressing this protein. Therefore, a p olyclonal antibody (8196) was raised against type II NOS from induced RAW 264.7 macrophages and used to investigate the expression of this e nzyme in human lung tissue. Anti-type II NOS antibody did not cross-re act with either neuronal (type I) or endothelial (type III) constituti ve NOS, whereas a 130-kDa protein was detected in cytosol from induced macrophages or liver removed from lipopolysaccharide (25 mg/kg)-treat ed rats. Cells or tissues that lacked NOS activity did not express imm unoreactive proteins. Similarly, in grossly normal human lung tissue, no immunoreactivity was detected with the anti-type II NOS antibody. I n contrast, strong immunoreactivity was detected in alveolar macrophag es present in lung tissue from a patient with bronchiectasis and acute bronchopneumonia. These data demonstrate that human alveolar macropha ges are able to express type II NOS and support a role for this enzyme in pulmonary inflammatory pathophysiology.