Surface-active phospholipid in muscle lymph and its lubricating and adhesive properties.

In order to investigate the role of phospholipid in facilitating lymph flow, "deep-thigh" lymph was collected from ten anesthetized dogs and analyzed for phospholipids using thin-layer chromatography. The lymph was found to be surface active at liquid and at solid surfaces at which it deposited a hydrophobic monolayer in vitro. Extracted phospholipid was found to be an effective release agent as a monolayer, reducing the force of adhesion of 5% protein solutions by 76% according to a standard test for tacky glues. The same monolayers were effective lubricants, reducing friction by 96%; while mixtures of the same phospholipids from synthetic sources gave similar results for release and lubrication. Surfaces in contact with extracellular fluid or lymph in vivo were found to be hydrophobic with a drop of saline on semitendinosus muscle fibers displaying a contact angle of 40.2 degrees +/- 7.2 degrees. The results are considered compatible with the hypothesis that surface-active phospholipid facilitates the flow of lymph; while it could also provide boundary lubrication for sliding of connective tissue in locomotion and for any relative movement of motor units in muscle contraction and fatigue.