Background: It has been confirmed that surface-active phospholipid (SAPL), or surfactant, lines the surface of peritoneum and serves as a release and lubricating agent. The most important component in SAPL is phosphatidylcholine. A previous animal study showed that a saturated phosphatidylcholine, dipalmitoyl-phosphatidylcholine, reduced the formation of surgical adhesion. Latest studies have indicated that the dominant SAPL species at some sites outside the lung are not saturated phosphatidylcholine but, rather, are unsaturated phosphatidylcholine.
Methods: High performance liquid chromatography was used to analyse the phosphatidylcholine profile of dialysate samples obtained from peritoneal dialysis patients. Friction tests were performed on dipalmitoyl-phosphatidylcholine and selected unsaturated phosphatidylcholine.
Results: It was discovered that unsaturated phosphatidylcholine was the dominant SAPL species inside the peritoneal cavity. They are palmitoyl-linoleoyl-phosphatidylcholine, palmitoyl-oleoylphosphatidylcholine and stearoylarachidonoylphosphatidylcholine. Most interestingly, there was no dipalmitoyl-phosphatidylcholine detected from these dialysate samples. The coefficients of static and dynamic friction from palmitoyllinoleoyl-phosphatidylcholine and palmitoyloleoyl-phosphatidylcholine were measured and found to be lower than that of dipalmitoyl-phosphatidylcholine.
Conclusion: The results from the current study reveal that unsaturated phosphatidylcholine is the endogenous species inside the peritoneal cavity. This discovery offers further evidence that the dominant SAPL species at non-lung sites are unsaturated phosphatidylcholine, not saturated phosphatidylcholine, strongly indicating the difference between phosphatidylcholine species distribution at lung and non-lung sites. Unsaturated phosphatidylcholine has better anti-friction and lubrication properties than dipalmitoyl-phosphatidylcholine. Unsaturated phosphatidylcholine-based SAPL pharmaceutical products should be developed and evaluated.