PTGER4 and endometriosis: Elevated MRP4 and PGT expression, particularly in epithelial glandular cells, may result in increased availability of PGE2 and PGF2α, which through engagement of their EP3, EP4, or FP receptors (also elevated in endometriosis) may activate intracellular signals such as the diacylglycerol or cyclic AMP pathways.