LC-MS/MS-analysis of prostaglandin E2 and D2 in microdialysis samples of rats

For the determination of prostaglandins in microdialysis samples, usually immunoassays are used. However, these assays may show cross-reactivity among various prostaglandins. To overcome this problem a specific method for the determination of prostaglandin E2 and D2 in rat microdialysis samples by using liquid chromatography-electrospay ionization-tandem mass spectrometry (LC-ESI-MS/MS) is described. Prostaglandin E2 and D2 were extracted from microdialysis samples with liquid-liquid extraction using deuterated prostaglandin D2, [2H4]-PGD2, as internal standard. Subsequently, prostaglandins were separated with a phenomenex Synergi Hydro-RP column and determined with a PE Sciex API 3000 mass spectrometer equipped with a turbo ion spray interface operating in negative ionization mode. The method showed a LLOQ of 25 pg/ml for prostaglandin E2 and 50 pg/ml for prostaglandin D2. The applicability of the method is shown in rat spinal cord microdialysis samples following peripheral nociceptive stimulation.