Analysis of eustachian surfactant and its function as a release agent.

Thin-layer chromatography has been used to confirm the presence of phospholipids in the eustachian tubes of dogs and rabbits, analysis showing less phosphatidylcholine but more phosphatidylethanolamine than in pulmonary surfactant. Extracts were surface active not only in reducing surface tension at liquid-air interfaces but in adsorption to hydrophilic solids (glass) to render them hydrophobic. According to a standard test of solid-to-solid adhesiveness, these adsorbed monolayers were found to reduce, by up to 94%, the force of adhesion between surfaces glued by albumin identified in the washings and present in middle-ear effusions. This capability of eustachian surfactant to act as a true release agent is discussed for its possible role in the cause of serous otitis, leading to the concept of an adverse protein-surfactant (adhesion:release) ratio.