Mucin production in the middle ear in response to lipopolysaccharides

OBJECTIVE: This study examined the response of middle ear tissue to establish the lowest dose of lipopolysaccharide to induce mucin production in a rat otitis media model, METHODS: Twenty-six male Sprague-Dawley rats' eustachian tubes were obstructed before transtympanic inoculation of the bulla tympanica with 35 mu L of Krebs Ringer or 1, 10, 100, or 1000 mu g/mL lipopolysaccharide. After 7 days the effusion and a lavage were collected for mucin ELISA measurement, and tissue was collected for histologic evaluation. RESULTS: Mucin secretion was significantly increased in the 100 mu g/mL 51.20 +/- 13.6 mu g/mL (SE) and 1000 mu g/mL 69.42 +/- 8.57 mu g/mL groups when compared with the Krebs Ringer control group 1.84 +/- 0.28 mu g/mL (P < 0.05). Histologic evaluation shows goblet cell metaplasia and hyperplasia in the middle ear epithelium in the 1000 and 100 mu g/mL groups, CONCLUSIONS: The histology and ELISA results suggest that a middle ear effusion is generated with a dose of lipopolysaccharide as low as 100 mu g/mL.