Sequential analysis of serum proteins in middle ear effusions. A study in rats with experimentally induced serous and purulent otitis media.

Two otomicroscopically well-defined types of otitis media (OM)--one culture-negative serous (SOM) and the other purulent (POM)--were induced in rats by mechanically obstructing the eustachian tube or by splitting the soft palate. Samples of middle ear effusions (MEE) produced and sera were characterized electrophoretically and immunochemically at 1, 2, 3, 4 and 6 weeks after inducing middle ear fluid. The levels of albumin, transferrin, IgG, IgG1, IgG2, IgM, IgA, and secretory IgA (S-IgA) were determined. All proteins increased 3- to 10-fold in the MEE of the SOM group, whereas the concentrations in the POM group were low. Concentrations of some of the MEE proteins were seen to increase during the course of SOM, while concentrations in the POM group appeared to diminish. The protein content of the MEE in SOM and POM changed dynamically during the observation period. These alterations differed between the two types of OM, reflecting the differing mechanisms that produce the MEE content. These findings indicate that sequential characterization of effusion material in animal OM models may elicit information which might allow staging of this complex disease clinically.