8-iso-15-keto PGF2α is a metabolite of the isoprostane 8-iso PGF2α in rabbits, monkeys, and humans. 8-isoprostane (8-iso PGF2α) is a prostaglandin-like product of non-specific lipid peroxidation. In both humans and monkeys, exogenously infused 8-iso PGF2α is converted primarily to metabolites having 2 or 4 carbon atoms removed from the top side chain by β-oxidation. A similar pattern is observed when tritiated 8-iso PGF2α is infused into rabbits. Early in the infusion (within 1-2 minutes) 8-iso -15-keto PGF2α was a major component of the metabolite profile, which was comprised mostly of unmetabolized 8-iso PGF2α. 8-iso -15-keto PGF2α is a vasoconstrictor when tested on the rat isolated thoracic aorta, acting via the TP (thromboxane) receptor.