Endogenous prostaglandin and primary product of arachidonic acid/cyclooxygenase pathway. Binds with high affinity to EP1, EP2, EP3 and EP4 receptors (Kd values range between ~ 1 - 10 nM). Influences a wide range of processes including inflammation, smooth muscle relaxation, fertility and gastric mucosal integrity. Regulates vertebrate hematopoietic stem cell (HSC) homeostasis.