LOCALIZATION OF EXTRACELLULAR-SUPEROXIDE DISMUTASE IN RAT LUNG - NEUTROPHILS AND MACROPHAGES AS CARRIERS OF THE ENZYME

Immunohistochemistry (IHC) and in situ hybridization (ISH) was used to localize extracellular superoxide dismutase (EC-SOD) and its mRNA in rat lung before and after a lipopolysaccharide (LPS)- and hyperoxia-in duced inflammation. In control rats, EC-SOD mRNA was synthesized in ma crophages and in cells of the arterial vessel walls and the alveolar s epta. The EC-SOD protein was mainly localized in plasma and on the api cal side of the epithelial cells located near bronchus-associated lymp hoid tissue (BALT). ISH did not reveal major changes in the distributi on of EC-SOD mRNA upon induction of inflammation. In contrast, IHC dem onstrated a progressive staining of the epithelium of the larger bronc hi for the protein. Neutrophils and macrophages invading the lung show ed an intensive staining for the EC-SOD protein concomitantly with a d ecrease of the enzyme in the plasma. Twenty-four hours after LPS stimu lation only a spotty positivity remained on neutrophils in and between the alveolar spaces. In the bronchoalveolar lavage fluid (BALF), only macrophages showed a strong positivity for EC-SOD mRNA while the prot ein was detected in macrophages and neutrophils. Exposure to hyperoxia did not affect the distribution of EC-SOD mRNA and protein. The prese nted data demonstrated that in lung tissue the EC-SOD enzyme may have a protective function for activated macrophages, neutrophils, and lymp oid tissue-associated epithelial cells. (C) 1998 Elsevier Science Inc.