Disaturated phosphatidylcholine in rabbit eustachian tube surfactant

A chemical analysis of phospholipids in rabbit Eustachian tube and in its lavages shows phosphatidylcholine (PC) as being the predominating compound, followed by sphingomyelin and phosphatidylethanolamine. As in the lung surfactant, the majority of tubal PC is represented by its disaturated form dipalmitoylphosphatidylcholine (DPPC), known as a powerful surface-active agent. The concentration of PC and DPPC is higher in tubal washing than in the whole tissue, suggesting the existence of an active secretory process. Incubation of tubal mucosa with 14C-choline resulted in the biosynthesis of radiolabelled PC and DPPC at a ratio similar to the lung. These data provide further evidence for the existence of a surface-active agent in the Eustachian tube, chemically similar to the lung surfactant and probably produced through similar metabolic pathways.