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 diseas e is often treated with insertion of ventilation tubes, which causes h yperoxia relative to the physiological state in the tympanic cavity. T he present study was undertaken to quantitate the interaction between endotoxin and relative hyperoxia in cultures of rabbit middle ear fibr oblasts incubated in normal middle ear gas and atmospheric air, respec tively. Growth was monitored by determination of DNA, cell protein and cell division. The synthetic activity was estimated by collagen produ ction. The antioxidant defense was determined by measuring the intra- and extracellular concentrations of superoxide dismutase (SOD): The re sults demonstrated that hyperoxia significantly impaired the growth of middle ear fibroblasts, which was compensated for by addition of endo toxin stimulating the growth. The collagen synthesis increased signifi cantly in atmospheric air with a synergistic effect of endotoxin. Hype roxia induced intracellular SOD formation, while endotoxin tended to r educe the synthesis. Finally exposure to atmospheric air caused signif icantly larger amounts of reducing agents extracellularly in cultures without endotoxin compared to endotoxin incubated cultures. It is sugg ested that endotoxin possesses both synergistic and antagonistic poten tial as regards the effects of relative hyperoxia, and that the intera ction between endotoxin and hyperoxia may be an important factor in ot itis media.