ATMOSPHERIC AIR VS NORMAL MIDDLE-EAR GAS - EFFECTS ON IN-VITRO GROWTHAND COLLAGEN-SYNTHESIS IN NORMAL MIDDLE-EAR FIBROBLASTS

The present study was undertaken to quantitate the effects of atmosphe ric air and normal middle ear gas on cultured fibroblasts obtained fro m normal rabbit middle ear mucosa. The cells were exposed to three dif ferent gas compositions: 7% O-2:5% CO2:88% N-2, 21% O-2:5% CO2:74% N-2 , and 75% O-2:5% CO2:20% N-2. The growth was monitored by measuring th e total content of cell protein, the amount of DNA, and the cell divis ion activity. The activity of the synthetic apparatus was determined b y the collagen synthesis. For comparison, rabbit skin fibroblasts were grown under identical conditions. The results demonstrated significan tly higher replication rate of middle ear fibroblasts at 7% oxygen tha n at atmospheric air whereas the collagen synthesis was significantly lower at 7%. Furthermore, the responses varied significantly between r abbit middle ear and rabbit skin fibroblasts. Thus the present study s ubstantiates the hypothesis of an influence of atmospheric air on the middle ear mucosa which might be of importance, e.g., in relation to i nsertion of ventilation tubes or longstanding perforations of the tymp anic membrane in otitis media.