Gel chromatographic characterization of proteins in mucous and serous middle ear effusions of patients with otitis media in comparison to serum proteins

Abstract

Otitis media with effusion (OME) is an inflammatory disease of the middle ear cavity that is associated with middle ear effusions (MEEs), which are frequently mucous and serous for pediatric and adult patients exhibiting low and high responsiveness to medical treatment, respectively. To assess the pathological outcomes in mucous and serous MEEs, their protein compositions were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting in comparison with those in the same patients’ sera. A mucin, which is immunochemically identical with nasal mucin, was a characteristic consituent of mucous MEEs (n = 25), being present at the concentration of 59.4 mg/ml and comprising about 60% of the total proteins, but it was not detected in serous MEEs (n = 30) or sera. Serum proteins with molecular weights of less than 260 kDa were detected in serous and mucous MEEs, in which albumin was the major protein. Albumin, IgM and α1-acid glycoprotein, and lysozyme, IgA and IgG in MEEs were present at lower and higher concentrations than in sera, respectively. The ratios of IgA, IgG, IgM and α1-acid glycoprotein to albumin in mucous MEEs were 4-, 3-, 1.4- and 1.0-times higher than those in the respective pediatric sera, and those in serous MEEs were 1.7-, 1.7-, 0.6- and 0.3-times higher than those in adult sera. Also, the concentrations of lysozyme in mucous and serous MEEs were 19 and 3 μg/ml, but those in pediatric and adult sera were negligible. These results indicate that the contents of these proteins, in comparison to albumin, might be useful criteria for assessing the inflammation level in MEEs.