A naturally occurring E-series prostaglandin produced by the COX metabolism of ω-3 arachidonic acid. It was first isolated and characterized as a product of ram seminal vesicle microsomes. The relative abundance of Δ17-PGE1 in humans and other animals is low in comparison with PGE2, and is likely to be a reflection of precursor fatty acid abundance in the phospholipid PUFA reservoir. Definitive studies on the biosynthesis of Δ17-PGE1 in intact animals have not been done. Δ17-PGE1 is about half as potent as PGE1 as an inhibitor of ADP-induced aggregation of rabbit PRP. In human PRP, Δ17-PGE1 is a more potent antiplatelet agonist than PGE1, with an IC50 of about 30 nM.3 The vascular effects of Δ17-PGE1 have not been reported.