title: Evolution of endotoxin-induced lung injury in the rat beyond the acute phase.
abstract: OBJECTIVE
  Intratracheal endotoxin in rats causes acute lung injury. Here we have addressed the cellular physiopathology of lung recovery from that injury.
  
  
  METHODS
  The lungs of 5 untreated rats and rats treated with intratracheal endotoxin from 2, 3, 5, 8 (5 rats each) and 15 days (2 rats) were studied by light and electron microscopy and immunohistochemistry.
  
  
  RESULTS
  In the acute phase there was a reduction in the aerated spaces (p < 0.01); diffuse infiltration of granulocytes and macrophages; hyperplasia of type-II pneumocytes, and hypertrophy of interstitial cells. Aerated spaces improved during recovery. In the early recovery phase (3-8 days) the compartmentalization of infiltrating cells varied significantly (p < 0.01): macrophages remained widespread while neutrophils were inside blood vessels. Many pneumocytes were intermediate between type-I and type-II cells. In the late recovery phase (15 days) the infiltrate disappeared; myofibroblasts were significantly more than previously (p < 0.01) and extracellular matrix was abundant; type-II pneumocytes contained non-lamellated lipid inclusions.
  
  
  CONCLUSIONS
  Macrophages play a pivotal role in the damage-repair processes of the lung following endotoxin injury, leading to an increase in extracellular matrix, differentiation of myofibroblasts and altered secretion of surfactant by newly differentiated type-II pneumocytes.
authors.affiliation: Department of Anatomy, Histology and Forensic Medicine, University of Florence, Florence, Italy. l.domenici@unifi.it
authors.forename: L
authors.initials: L
authors.lastname: Domenici
authors.forename: L
authors.initials: L
authors.lastname: Pieri
authors.forename: M B
authors.initials: MB
authors.lastname: Gallè
authors.forename: P
authors.initials: P
authors.lastname: Romagnoli
authors.forename: C
authors.initials: C
authors.lastname: Adembri
mesh_terms: D000818:Animals; D002908:Chronic Disease; D004195:Disease Models, Animal; D004731:Endotoxins / Q000633:toxicity*; D004847:Epithelial Cells / Q000473:pathology; D005109:Extracellular Matrix / Q000473:pathology; D005347:Fibroblasts / Q000473:pathology; D006098:Granulocytes / Q000276:immunology; D007150:Immunohistochemistry; D008168:Lung / Q000187:drug effects* / Q000473:pathology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D011663:Pulmonary Surfactants / Q000378:metabolism; D051381:Rats; D012128:Respiratory Distress Syndrome / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology*
chemical_list: D004731:Endotoxins; D011663:Pulmonary Surfactants