The influence of endotoxin upon middle ear fibroblasts cultured in normal middle ear gas and atmospheric air.
Otitis media represents a continuum of inflammatory stages frequently in association with bacteria and/or endotoxin. Furthermore, the disease is often treated with insertion of ventilation tubes, which causes hyperoxia relative to the physiological state in the tympanic cavity. The present study was undertaken to quantitate the interaction between endotoxin and relative hyperoxia in cultures of rabbit middle ear fibroblasts incubated in normal middle ear gas and atmospheric air, respectively. Growth was monitored by determination of DNA, cell protein and cell division. The synthetic activity was estimated by collagen production. The antioxidant defense was determined by measuring the intra-and extracellular concentrations of superoxide dismutase (SOD). The results demonstrated that hyperoxia significantly impaired the growth of middle ear fibroblasts, which was compensated for by addition of endotoxin stimulating the growth. The collagen synthesis increased significantly in atmospheric air with a synergistic effect of endotoxin. Hyperoxia induced intracellular SOD formation, while endotoxin tended to reduce the synthesis. Finally, exposure to atmospheric air caused significantly larger amounts of reducing agents extracellularly in cultures without endotoxin compared to endotoxin incubated cultures. It is suggested that endotoxin possess both synergistic and antagonistic potential as regards the effects of relative hyperoxia, and that the interaction between endotoxin and hyperoxia may be an important factor in otitis media.
Ovesen
T
T
Research Laboratory for Biochemical Pathology, Aarhus University Hospital, Denmark.
Gaihede
M
M
Elbrønd
O
O
D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis; D004247:DNA / Q000096:biosynthesis; D004432:Ear, Middle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D004731:Endotoxins / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D010033:Otitis Media / Q000378:metabolism / Q000473:pathology; D010100:Oxygen / Q000502:physiology*; D011817:Rabbits; D013482:Superoxide Dismutase / Q000096:biosynthesis
D004731:Endotoxins; D003094:Collagen; D004247:DNA; D013482:Superoxide Dismutase; D010100:Oxygen