EP₂, EP₃, and EP₄ are expressed on human mast cells. At low doses prostaglandin E₂ inhibits mannitol mast cell degranulation.

<p>Real time PCR was performed in LAD2 cells using EP receptor probes as indicated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110870#pone-0110870-t001" target="_blank">Table 1</a> (A). The EP receptors expression levels were normalized with the β-actin expression level, EP₁ expression was undetectable. Western blot analysis was carried out with specific antibodies against EP₁, EP₂, EP₃, and EP₄ in whole cell lysates from CD34⁺ derived mast cells and LAD2 cells; blot against β-actin was performed as a loading control (B). PGE₂ titration was carried out before 10% mannitol stimulation in LAD2 cells (C). The experiments are representative of 3 independent assays. Statistical significance (*p≤0.05) is relative to mannitol-stimulated cells.