PGE1 is not a major naturally occurring PG, but is widely administered clinically for several indications including peripheral occlusive vascular disease, erectile dysfunction, and in neonatal cardiology. COX metabolism of the unusual fatty acid 10,13,16-docosatrienoic acid yields 1a,1b-dihomo PGE1. This rare metabolite has been recovered from incubations of whole sheep seminal vesicles, but has not been reported in humans. In ex vivo preparations of rat aorta and rat PRP, 1a,1b-dihomo PGE1 was found to be much less active than PGE1 itself.