Atmospheric air vs. normal middle ear gas: effects on in vitro growth and collagen synthesis in normal middle ear fibroblasts.

The present study was undertaken to quantitate the effects of atmospheric air and normal middle ear gas on cultured fibroblasts obtained from normal rabbit middle ear mucosa. The cells were exposed to three different gas compositions: 7% O2:5% CO2:88% N2, 21% O2:5% CO2:74% N2, and 75% O2:5% CO2:20% N2. The growth was monitored by measuring the total content of cell protein, the amount of DNA, and the cell division activity. The activity of the synthetic apparatus was determined by the collagen synthesis. For comparison, rabbit skin fibroblasts were grown under identical conditions. The results demonstrated significantly higher replication rate of middle ear fibroblasts at 7% oxygen than at atmospheric air whereas the collagen synthesis was significantly lower at 7%. Furthermore, the responses varied significantly between rabbit middle ear and rabbit skin fibroblasts. Thus the present study substantiates the hypothesis of an influence of atmospheric air on the middle ear mucosa which might be of importance, e.g., in relation to insertion of ventilation tubes or longstanding perforations of the tympanic membrane in otitis media.